fix: 生产安全检查 — 鉴权 + 资金安全 + Slot TTL

1. upload.py: /video /audio 端点添加 get_current_user 鉴权
2. caption.py: /ata/align 端点添加 get_current_user 鉴权
3. points.py: allow_negative 硬编码 False，禁止客户端控制欠费
4. slot_manager.py: TTL 1800s → 1200s，减少异常崩溃后的槽位泄漏时间
5. points.py: 顺手修复 ruff UP017（timezone.utc → UTC）

python-api/app/api/v1/caption.py

@@ -7,9 +7,11 @@
 
 import logging
 
-from fastapi import APIRouter, HTTPException, Request
+from fastapi import APIRouter, Depends, HTTPException, Request
 
+from app.api.deps import get_current_user
 from app.core.exceptions import PlatformError
+from app.models.user import User
 from app.schemas.caption import (
     AutoAlignSubmitRequest,
 )
@@ -36,7 +38,12 @@ router = APIRouter(prefix="/caption", tags=["Caption"])
 
 
 @router.post("/ata/align")
-async def auto_align_caption(request_body: AutoAlignSubmitRequest, request: Request, max_wait_time: int = 120):
+async def auto_align_caption(
+    request_body: AutoAlignSubmitRequest,
+    request: Request,
+    max_wait_time: int = 120,
+    current_user: User = Depends(get_current_user),
+):
     """
     自动字幕打轴（完整流程）