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/entrypoint.sh

@@ -0,0 +1,31 @@
+#!/bin/sh
+
+# 等待数据库就绪
+echo "Waiting for database..."
+sleep 5
+
+# 执行数据库迁移
+echo "Running database migrations..."
+python manage.py migrate --noinput
+
+# 收集静态文件
+echo "Collecting static files..."
+python manage.py collectstatic --noinput
+
+# 计算worker数量 (CPU核心数 * 2 + 1)
+WORKERS=$(python -c 'import multiprocessing; print(multiprocessing.cpu_count() * 2 + 1)')
+
+# 启动 Gunicorn
+echo "Starting Gunicorn with $WORKERS workers..."
+exec gunicorn api.asgi:application \
+    --bind 0.0.0.0:8000 \
+    --worker-class uvicorn.workers.UvicornWorker \
+    --workers $WORKERS \
+    --threads 2 \
+    --timeout 120 \
+    --max-requests 1000 \
+    --max-requests-jitter 50 \
+    --keep-alive 5 \
+    --log-level error \
+    --capture-output \
+    --enable-stdio-inheritance