fix(test): correct TypeScript types in frontend test mocks

- Use RSS type instead of non-existent RSSItem/RSSResponse
- Add expire field to mockLoginSuccess
- Replace offset with episode_offset/season_offset in mockBangumiAPI
- Add needs_review_reason field to mockBangumiAPI
- Add missing RSS fields (connection_status, last_checked_at, last_error)
- Fix generic types in test utilities

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: EstrellaXD