fix(pipeline): add redis+libretranslate to homelab, make Asynq enqueue errors non-fatal

- homelab/docker-compose.yml: add redis:7-alpine service (port 6379 bound to host
  so Caddy TLS proxy on prod can reach it), add libretranslate service, add
  redis_data and libretranslate_data volumes
- asynqqueue/producer.go: Asynq enqueue failures are now logged as warnings instead
  of returned as errors — PB record already exists so runner picks it up via poll
- backend/main.go: pass logger to NewProducer

Root cause: Redis was not reachable at 192.168.0.109:6379 because the redis
container had no host port binding. Caddy TLS proxy terminates TLS but could
not TCP-connect to the backend Redis.

homelab/docker-compose.yml

@@ -289,6 +289,48 @@ services:
       timeout: 5s
       retries: 5
 
+  # ── Redis (Asynq task queue) ────────────────────────────────────────────────
+  # Dedicated Redis instance for Asynq job dispatch.
+  # The prod backend enqueues jobs via redis.libnovel.cc:6380 (Caddy TLS proxy →
+  # host:6379). The runner reads from this instance directly on the Docker network.
+  # Port is bound to 0.0.0.0:6379 so the Caddy layer4 proxy on prod can reach it.
+  redis:
+    image: redis:7-alpine
+    restart: unless-stopped
+    command: ["redis-server", "--appendonly", "yes", "--requirepass", "${REDIS_PASSWORD}"]
+    ports:
+      - "6379:6379"
+    volumes:
+      - redis_data:/data
+    healthcheck:
+      test: ["CMD", "redis-cli", "-a", "${REDIS_PASSWORD}", "ping"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+
+  # ── LibreTranslate ──────────────────────────────────────────────────────────
+  # Self-hosted machine translation. Runner connects via http://libretranslate:5000.
+  # Only English → configured target languages are loaded to save RAM.
+  libretranslate:
+    image: libretranslate/libretranslate:latest
+    restart: unless-stopped
+    environment:
+      LT_API_KEYS: "true"
+      LT_API_KEYS_DB_PATH: "/app/db/api_keys.db"
+      LT_LOAD_ONLY: "en,ru,id,pt,fr"
+      LT_DISABLE_WEB_UI: "true"
+      LT_UPDATE_MODELS: "false"
+    expose:
+      - "5000"
+    volumes:
+      - libretranslate_data:/app/db
+    healthcheck:
+      test: ["CMD", "curl", "-sf", "http://localhost:5000/languages"]
+      interval: 30s
+      timeout: 10s
+      retries: 5
+      start_period: 60s
+
   # ── Valkey ──────────────────────────────────────────────────────────────────
   # Used by GlitchTip for task queuing.
   valkey:
@@ -469,6 +511,8 @@ services:
 
 volumes:
   postgres_data:
+  redis_data:
+  libretranslate_data:
   valkey_data:
   uptime_kuma_data:
   gotify_data: