refactor: 移除 2FA 功能与三个冗余依赖

2FA 早已是死代码：TOTP 相关端点标注为前端未调用，前端唯一的
two_factor_auth 是硬编码 false，没有任何入口能打开它。

- 删除 TwoFactorAuthAPI、CheckTFARequiredAPI、_totp* 辅助函数、
  TwoFactorAuthCodeSerializer 及各 serializer 的 tfa_code 字段
- 删除管理端写 two_factor_auth/tfa_token 的分支。登录已不再校验
  TOTP，若保留写入路径，置 True 会变成静默的安全降级
- 删除 User.two_factor_auth / tfa_token 字段（迁移 0009）
- 移除 django-dbconn-retry：仅挂在 INSTALLED_APPS，代码零引用。
  DATABASES 未配置 CONN_MAX_AGE（默认 0），本就没有持久连接需要
  重连修复。要开持久连接用 Django 自带的 CONN_HEALTH_CHECKS
- requests 换成 httpx（openai 已经引入）：删除废弃的
  ReleaseNotesAPI，judge dispatcher 显式传 timeout=None 以保持
  requests 原本的无超时行为，判题请求是同步等结果的

依赖净减 5 个：otpauth、qrcode、requests、charset-normalizer、
django-dbconn-retry

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

deploy/requirements.txt

@@ -1,5 +1,5 @@
 # This file was autogenerated by uv via the following command:
-#    uv export --format requirements.txt --no-dev -o deploy/requirements.txt
+#    uv export --format requirements.txt
 annotated-types==0.7.0 \
     --hash=sha256:1f02e8b43a8fbbc3f3e0d4f0f4bfc8131bcb4eebe8849b8e5c773f3a1c582a53 \
     --hash=sha256:aff07c09a53a08bc8cfccb9c85b05f1aa9a2a6f23728d790723543408344ce89
@@ -25,7 +25,6 @@ certifi==2026.4.22 \
     # via
     #   httpcore
     #   httpx
-    #   requests
     #   sentry-sdk
 channels==4.3.2 \
     --hash=sha256:f2bb6bfb73ad7fb4705041d07613c7b4e69528f01ef8cb9fb6c21d9295f15667 \
@@ -37,62 +36,6 @@ channels-redis==4.3.0 \
     --hash=sha256:48f3e902ae2d5fef7080215524f3b4a1d3cea4e304150678f867a1a822c0d9f5 \
     --hash=sha256:740ee7b54f0e28cf2264a940a24453d3f00526a96931f911fcb69228ef245dd2
     # via onlinejudge
-charset-normalizer==3.4.9 \
-    --hash=sha256:0327fcd59a935777d83410750c50600ee9571af2846f71ce40f25b13da1ef380 \
-    --hash=sha256:03d07803992c6c7bbc976327f34b18b6160327fc81cb82c9d504720ac0be3b62 \
-    --hash=sha256:0d861473f743244d349b50f850d10eb87aeb22bbdcc8e64f79273c94af5a8226 \
-    --hash=sha256:16b65ea0f2465b6fb52aa22de5eca612aa964ddfec00a912e26f4656cbef890b \
-    --hash=sha256:19ac87f93086ce37b86e098888555c4b4bc48102279bae3350098c0ed664b501 \
-    --hash=sha256:21e764fd1e70b6a3e205a0e46f3051701f98a8cb3fad66eeb80e48bb502f8698 \
-    --hash=sha256:32286a2c8d167e897177b673176c1e3e00d4057caf5d2b64eef9a3666b03018e \
-    --hash=sha256:33bdcc2a32c0a0e861f60841a512c8acc658c87c2ac59d89e3a46dacf7d866e4 \
-    --hash=sha256:40a126142a56b2dfc0aacbad1de8310cbf60da7656db0e6b16eebd48e3e93519 \
-    --hash=sha256:416c229f77e5ea25b3dfd4b582f8d73d7e43c22320302b9ab128a2d3a0b38efe \
-    --hash=sha256:440eede837960000d74978f0eba527be106b5b9aee0daf779d395276ed0b0614 \
-    --hash=sha256:45b0cc4e3556cd875e09102988d1ab8356c998b596c9fced84547c8138b487a0 \
-    --hash=sha256:4b3dac63058cc36820b0dd072f89898604e2d39686fe05321729d00d8ac185a0 \
-    --hash=sha256:4d1c96a7a18b9690a4d46df09e3e3382406ae3213727cd1019ebade1c4a81917 \
-    --hash=sha256:51307f5c71007673a2bf8232ad973483d281e74cb99c8c5a990af1eefa6277d9 \
-    --hash=sha256:51447e9aa2684679af07ca5021c3db526e0284347ebf4ffcec1154c3350cfe32 \
-    --hash=sha256:5b10cd92fc5c498b35a8635df6d5a100207f88b63a4dc1de7ef9a548e1e2cd63 \
-    --hash=sha256:5e226f6218febc71f6c1fc2fafb91c226f75bdc1d8fb12d66823716e891608fd \
-    --hash=sha256:609b3ba8fcc0fb5ab7af00719d0fb6ad0cb518e48e7712d12fd68f1327951198 \
-    --hash=sha256:60f44ade2cf573dad7a277e6f8ca9a51a21dda572b13bd7d8539bb3cd5dbedde \
-    --hash=sha256:611057cc5d5c0afc743ba8be6bd828c17e0aaa8643f9d0a9b9bb7dea80eb8012 \
-    --hash=sha256:673611bbd43f0810bec0b0f028ddeaaa501190339cac411f347ac76917c3ae7b \
-    --hash=sha256:68e5f26a1ad57ded6d1cfb85331d1c1a195314756471d97758c48498bb4dcdf5 \
-    --hash=sha256:69b157c5d3292bcd443faca052f3096f637f1e074b98212a933c074ae23dc3b8 \
-    --hash=sha256:75286256590a6320cf106a0d28970d3560aad9ee09aa7b34fb40524792436d35 \
-    --hash=sha256:78841cccf1af7b40f6f716338d50c0902dbe88d9f800b3c973b7a9a0a693a642 \
-    --hash=sha256:78fa18e436a1a0e58dbd7e02fc4473f3f32cceb12df9dfca542d075961c307d2 \
-    --hash=sha256:7b86a2b16095d250c6f58b3d9b2eee6f4147754344f3dab0922f7c9bf7d226c9 \
-    --hash=sha256:83aed2c10721ddd90f68140685391b50811a880af20654c59af6b6c66c40513c \
-    --hash=sha256:84fd18bcc17526fc2b3c1af7d2b9217d32c9c04448c16ec693b9b4f1985c3d33 \
-    --hash=sha256:898f0e9068ca27d37f8e83a5b962821df851532e6c4a7d615c1c033f9da6eedf \
-    --hash=sha256:8a79d9f4d8001473a30c163556b3c3bfebec837495a412dde78b51672f6134f9 \
-    --hash=sha256:90c44bc373b7687f6948b693cceaea1348ae0975d7474746559494468e3c1d84 \
-    --hash=sha256:9104ed0bd76a429d46f9ec0dbc9b08ad1d2dcdf2b00a5a0daa1c145329b35b44 \
-    --hash=sha256:9b2aff1c7b3884512b9512c3eaadd9bab39fb45042ffaaa1dd08ff2b9f8109d9 \
-    --hash=sha256:9b8e0f3107e2200b76f6054de99016eac3ee6762713587b36baaa7e4bd2ae177 \
-    --hash=sha256:9cdef90ae47919cae358d8ab15797a800ed41da7aba5d72419fb510729e2ed4b \
-    --hash=sha256:a1786910334ed46ab1dd73222f2cd1e05c2c3bb39f6dddb4f8b36fc382058a39 \
-    --hash=sha256:a4cfde78a9f2880208d16a93b795726a3017d5977e08d1e162a7a31322479c41 \
-    --hash=sha256:a4fbdde9dd4a9ce5fd52c2b3a347bb50cc89483ef783f1cb00d408c13f7a96c0 \
-    --hash=sha256:bd47ba7fc3ca94896759ea0109775132d3e7ab921fbf54038e1bab2e46c313c9 \
-    --hash=sha256:c1c948747b03be832dceed96ca815cef7360de9aa19d37c730f8e3f6101aca48 \
-    --hash=sha256:c25fe15c70c59eb7c5ce8c06a1f3fa1da0ecc5ea1e7a5922c40fd2fa9b0d5046 \
-    --hash=sha256:cc1b0fff8ead343dae06305f954eb8468ba0ec1a97881f42489d198e4ce3c632 \
-    --hash=sha256:cd6c3d4b783c556fa00bf540854e42f135e2f256abd29669fcd0da0f2dec79c2 \
-    --hash=sha256:d4d6fcde76f94f5cb9e43e9e9a61f16dacefd228cbbf6f1a09bd9b219a92f1a1 \
-    --hash=sha256:df115d4d83168fdf2cae48ef1ff6d1cb4c466364e30861b37121de0f3bf1b990 \
-    --hash=sha256:e4fd89cc178bced6ad29cb3e6dd4aa63fa5017c3524dbd0b25998fb64a87cc8b \
-    --hash=sha256:ee2f2a527e3c1a6e6411eb4209642e138b544a2d72fe5d0d76daf77b24063534 \
-    --hash=sha256:f7fb7d750cfa0a070d2c24e831fd3481019a60dd317ea2b39acbcebc08b6ed81 \
-    --hash=sha256:f840ed6d8ecba8255df8c42b87fadeda98ddfc6eeec05e2dc66e26d46dd6f58a \
-    --hash=sha256:f86c6358749bd4fda175388691e3ba8c46e24c5347d0afd20f9b7edfc9faf07d \
-    --hash=sha256:fa36ec09ef71d158186bc79e359ff5fdd6e7996fe8ab638f00d6b93139ba4fcf \
-    --hash=sha256:fe2c7201c642b7c308f1675355ad7ff7b66acfe3541625efe5a3ad38f29d6115
-    # via requests
 click==8.4.1 \
     --hash=sha256:482be17c6991b8c19c5429a1e995d9b0efdbb63172824c41f99965dc0ade8ec2 \
     --hash=sha256:918b5633eddf6b41c32d4f454bf0de810065c74e3f7dbf8ee5452f8be88d3e96
@@ -102,7 +45,6 @@ colorama==0.4.6 ; sys_platform == 'win32' \
     --hash=sha256:4f1d9991f5acc0ca119f9d443620b77f9d6b33703e51011c16baf57afb285fc6
     # via
     #   click
-    #   qrcode
     #   tqdm
     #   uvicorn
 distro==1.9.0 \
@@ -119,9 +61,6 @@ django==6.0.4 \
     #   djangorestframework
     #   onlinejudge
     #   sentry-sdk
-django-dbconn-retry==0.3.1 \
-    --hash=sha256:d4b64d915440c3e5902ef8edf836366a6f4c4f027d34902135d7335233d6dbba
-    # via onlinejudge
 django-dramatiq==0.15.0 \
     --hash=sha256:23f0bc418a860952adbf822c4aa3b9c46c51d3d9f50be0a8ed3d19a53380df1d \
     --hash=sha256:e3cf1b2ac288fe4a7aa198c9450fe242ed312df8850f3f9e18ce01b8acc78b96
@@ -188,14 +127,15 @@ httptools==0.8.0 \
 httpx==0.28.1 \
     --hash=sha256:75e98c5f16b0f35b567856f597f06ff2270a374470a5c2392242528e3e3e42fc \
     --hash=sha256:d909fcccc110f8c7faf814ca82a9a4d816bc5a6dbfea25d6591d6985b8ba59ad
-    # via openai
+    # via
+    #   onlinejudge
+    #   openai
 idna==3.13 \
     --hash=sha256:585ea8fe5d69b9181ec1afba340451fba6ba764af97026f92a91d4eef164a242 \
     --hash=sha256:892ea0cde124a99ce773decba204c5552b69c3c67ffd5f232eb7696135bc8bb3
     # via
     #   anyio
     #   httpx
-    #   requests
 jieba==0.42.1 \
     --hash=sha256:055ca12f62674fafed09427f176506079bc135638a14e23e25be909131928db2
     # via onlinejudge
@@ -309,10 +249,6 @@ openai==2.34.0 \
     --hash=sha256:828b4efcbb126352c2b5eb97d33ae890c92a71ab72511aefc1b7fe64aeccb07b \
     --hash=sha256:c996a71b1a210f3569844572ad4c609307e978515fb76877cf449b72596e549e
     # via onlinejudge
-otpauth==2.2.1 \
-    --hash=sha256:169a7adbd715fca687f6a66d02ccdbefc229fb49f8a634b958d286f908134d59 \
-    --hash=sha256:b7eabe0ed91cb67eb3054b7f517e4b4a7495fb30eaf2951897d41c8feef5de73
-    # via onlinejudge
 packaging==26.2 \
     --hash=sha256:5fc45236b9446107ff2415ce77c807cee2862cb6fac22b8a73826d0693b0980e \
     --hash=sha256:ff452ff5a3e828ce110190feff1178bb1f2ea2281fa2075aadb987c2fb221661
@@ -540,20 +476,31 @@ pyyaml==6.0.3 \
     --hash=sha256:f7057c9a337546edc7973c0d3ba84ddcdf0daa14533c2065749c9075001090e6 \
     --hash=sha256:fc09d0aa354569bc501d4e787133afc08552722d3ab34836a80547331bb5d4a0
     # via uvicorn
-qrcode==8.2 \
-    --hash=sha256:16e64e0716c14960108e85d853062c9e8bba5ca8252c0b4d0231b9df4060ff4f \
-    --hash=sha256:35c3f2a4172b33136ab9f6b3ef1c00260dd2f66f858f24d88418a015f446506c
-    # via onlinejudge
 redis==7.4.0 \
     --hash=sha256:64a6ea7bf567ad43c964d2c30d82853f8df927c5c9017766c55a1d1ed95d18ad \
     --hash=sha256:a9c74a5c893a5ef8455a5adb793a31bb70feb821c86eccb62eebef5a19c429ec
     # via
     #   channels-redis
     #   django-redis
-requests==2.34.2 \
-    --hash=sha256:2a0d60c172f83ac6ab31e4554906c0f3b3588d37b5cb939b1c061f4907e278e0 \
-    --hash=sha256:f288924cae4e29463698d6d60bc6a4da69c89185ad1e0bcc4104f584e960b9ed
-    # via onlinejudge
+ruff==0.15.12 \
+    --hash=sha256:01da3988d225628b709493d7dc67c3b9b12c0210016b08690ef9bd27970b262b \
+    --hash=sha256:2849ea9f3484c3aca43a82f484210370319e7170df4dfe4843395ddf6c57bc33 \
+    --hash=sha256:83b2f4f2f3b1026b5fb449b467d9264bf22067b600f7b6f41fc5958909f449d0 \
+    --hash=sha256:84a1630093121375a3e2a95b4a6dc7b59e2b4ee76216e32d81aae550a832d002 \
+    --hash=sha256:9ba3b8f1afd7e2e43d8943e55f249e13f9682fde09711644a6e7290eb4f3e339 \
+    --hash=sha256:9cae0f92bd5700d1213188b31cd3bdd2b315361296d10b96b8e2337d3d11f53e \
+    --hash=sha256:9e77c7e51c07fe396826d5969a5b846d9cd4c402535835fb6e21ce8b28fef847 \
+    --hash=sha256:a538f7a82d061cee7be55542aca1d86d1393d55d81d4fcc314370f4340930d4f \
+    --hash=sha256:b0c862b172d695db7598426b8af465e7e9ac00a3ea2a3630ee67eb82e366aaa6 \
+    --hash=sha256:c87a162d61ab3adca47c03f7f717c68672edec7d1b5499e652331780fe74950d \
+    --hash=sha256:d0185894e038d7043ba8fd6aee7499ece6462dc0ea9f1e260c7451807c714c20 \
+    --hash=sha256:dd8aed930da53780d22fc70bdf84452c843cf64f8cb4eb38984319c24c5cd5fd \
+    --hash=sha256:e3bcd123364c3770b8e1b7baaf343cc99a35f197c5c6e8af79015c666c423a6c \
+    --hash=sha256:e852ba9fdc890655e1d78f2df1499efbe0e54126bd405362154a75e2bde159c5 \
+    --hash=sha256:ecea26adb26b4232c0c2ca19ccbc0083a68344180bba2a600605538ce51a40a6 \
+    --hash=sha256:f86f176e188e94d6bdbc09f09bfd9dc729059ad93d0e7390b5a73efe19f8861c \
+    --hash=sha256:fb129f40f114f089ebe0ca56c0d251cf2061b17651d464bb6478dc01e69f11f5 \
+    --hash=sha256:fe87510d000220aa1ed530d4448a7c696a0cae1213e5ec30e5874287b66557b5
 sentry-sdk==2.59.0 \
     --hash=sha256:abcf65ee9a9d9cdebf9ad369782408ecca9c1c792686ef06ba34f5ab233527fe \
     --hash=sha256:cd265808ef8bf3f3edf69b527c0a0b2b6b1322762679e55b8987db2e9584aec1
@@ -643,9 +590,7 @@ tzdata==2026.2 ; sys_platform == 'win32' \
 urllib3==2.6.3 \
     --hash=sha256:1b62b6884944a57dbe321509ab94fd4d3b307075e0c2eae991ac71ee15ad38ed \
     --hash=sha256:bf272323e553dfb2e87d9bfd225ca7b0f467b919d7bbd355436d3fd37cb0acd4
-    # via
-    #   requests
-    #   sentry-sdk
+    # via sentry-sdk
 uvicorn==0.48.0 \
     --hash=sha256:48097851328b87ec36117d3d575234519eb58c2b22d79666e9bbc6c49a761dad \
     --hash=sha256:a5504207195d08c2511bf9125ede5ac4a4b71725d519e758d01dcf0bc2d31c37