fix: address code review findings

- Store cached_at in canonical UTC layout so the cache TTL cutoff comparison is a valid time ordering (previously go-sqlite3 serialized time.Time as RFC3339, making the space-separated cutoff match only by ASCII accident; same-day expired entries were falsely served as fresh).

- Remove stale no-op scanner config keys (ignore_bootlegs, include_compilations) from config.yaml.example and docs; these fields were removed from ScannerConfig but left in configs, silently doing nothing.

docs/Specification.md

@@ -147,8 +147,6 @@ telegram:
 
 scanner:
   fuzzy_threshold: 0.85
-  ignore_bootlegs: true
-  include_compilations: true
 ```