Add a two-level caching architecture for debrid service availability lookups:
- L1: Redis (existing) with 10-day TTL for fast in-memory access
- L2: PostgreSQL with 30-day TTL for persistent caching across Redis restarts
Changes:
- Add `debrid_cache` table with unique constraint on (info_hash, service) and indexes for efficient queries
- Create `DebridCacheDAO` with batch get/upsert and invalidation methods
- Add pgCron job to periodically clean up expired cache entries
- Extend `get_availability_bulk_cached` to check PG on Redis miss, warm Redis from PG hits, and write confirmed-cached results to PG
- Add `invalidate_availability_cache` method to remove false positives from both caches when NO_CACHE_VIDEO_URL is returned during playback
- Integrate `db_session` dependency into playback and search views
- Add retry handling to Yggflix API (3 retries, ignore Retry-After headers) and rate-limiting delay (0.3s) between consecutive queries
