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>

deploy/config.yaml

@@ -188,4 +188,10 @@ generation:
   worker_concurrency: 8
   stream_enabled: false
   article_timeout: 8m
+  task_lease_ttl: 10m
+  task_recovery_interval: 1m
+  task_recovery_timeout: 30s
+  task_recovery_batch_size: 100
+  task_queued_stale_after: 2m
+  task_max_attempts: 3
   

deploy/k3s/config/config.yaml

@@ -145,3 +145,9 @@ generation:
   worker_concurrency: 8
   stream_enabled: false
   article_timeout: 8m
+  task_lease_ttl: 10m
+  task_recovery_interval: 1m
+  task_recovery_timeout: 30s
+  task_recovery_batch_size: 100
+  task_queued_stale_after: 2m
+  task_max_attempts: 3