fix: resolve 10 code review issues

High priority:
- Fix concurrent race condition for view_count/like_count (atomic update)
- Add route request ID tracking to prevent race conditions
- Filter get_joke by status=approved (no pending content leak)
- Add error feedback for like button

Performance:
- Optimize random joke query (avoid full table sort)
- Limit page_size max to 100 (DoS prevention)

Medium:
- Add localStorage quota error handling
- Handle empty AI response gracefully
- Fix generate content title extraction

Low:
- Add rejected_jokes to stats API
- Update dashboard to show rejected count

__joke.json

@@ -0,0 +1 @@
+{"title":"程序员的幽默","content":"程序员去相亲，女方问：你有什么优点？程序员答：我bug少。女方：...","type_id":2,"crowd_id":2,"id":1,"status":"approved","view_count":2,"like_count":0,"created_at":"2026-05-21T14:05:38","updated_at":"2026-05-22T10:40:03","type_name":"谐音梗","crowd_name":"职场"}