chore: 将后端移动到 api/ 目录，准备合并为单仓库

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/submission/management/commands/classify_messages.py

@@ -0,0 +1,28 @@
+from django.core.management.base import BaseCommand
+
+from prompt.models import Conversation
+from submission.classifier import classify_conversation_messages
+
+
+class Command(BaseCommand):
+    help = "为所有缺失 Bloom 等级的用户消息补全分类"
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            "--force",
+            action="store_true",
+            help="重新分类所有消息（包括已有等级的）",
+        )
+
+    def handle(self, *args, **options):
+        force = options["force"]
+        convs = Conversation.objects.all()
+        total = convs.count()
+        self.stdout.write(f"共 {total} 个对话，开始分类...")
+
+        for i, conv in enumerate(convs, 1):
+            classify_conversation_messages(conv.id, force=force)
+            self.stdout.write(f"[{i}/{total}] {conv}", ending="\r")
+            self.stdout.flush()
+
+        self.stdout.write(self.style.SUCCESS(f"\n完成，处理了 {total} 个对话。"))