feat(cache,worker): overhaul cache layer and add generation task lease recovery

- shared/cache: add Options/L1/async/metrics/prefix decorators, multi-key ops, Redis pool tuning, and JSON readthrough metrics
- worker-generate: claim tasks via DB lease + heartbeat, requeue stale queued tasks, expire dead leases with refund/cache invalidation
- tenant: version article cache keys so worker recovery invalidations propagate cleanly
- shared/config: expand Redis (pool/timeouts/TLS) and Generation (lease/recovery) configs with defaults

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/app/knowledge_service.go

@@ -933,7 +933,7 @@ func (s *KnowledgeService) logKnowledgeResolve(
 		zap.Int("candidate_count", len(candidates)),
 		zap.Int("selected_count", len(selected)),
 		zap.Int("precise_fact_count", len(knowledgeCtx.PreciseFacts)),
-		zap.Strings("precise_facts", summarizeKnowledgeFactsForLog(knowledgeCtx.PreciseFacts)),
+		// zap.Strings("precise_facts", summarizeKnowledgeFactsForLog(knowledgeCtx.PreciseFacts)),
 	)
 }