fix(infra): move Redis to prod, fix LibreTranslate config loading

- Add Redis sidecar to prod docker-compose; backend connects locally (redis:6379)
- Caddy layer4 now proxies redis.libnovel.cc:6380 → local redis:6379 (not homelab LAN)
- Remove HOMELAB_REDIS_ADDR; homelab runner connects out to prod Redis via rediss://
- Remove local Redis from homelab runner compose; drop redis_data volume
- Fix config.Load() missing LibreTranslate section — LIBRETRANSLATE_URL was never read

Caddyfile

@@ -58,9 +58,9 @@
 
 	# ── Redis TCP proxy via layer4 ────────────────────────────────────────────
 	# Exposes prod Redis over TLS for Asynq job enqueueing from the homelab runner.
-	# Listens on :6380 (all interfaces). TLS is terminated here using the cert
+	# Listens on :6380 (all interfaces). TLS is terminated here using the cert
 	# for redis.libnovel.cc; traffic is proxied to the local Redis sidecar.
-	# Requires the caddy-l4 module in the custom Caddy build.
+	# Requires the caddy-l4 module in the custom Caddy build.
 	layer4 {
 		:6380 {
 			route {
@@ -73,7 +73,7 @@
 				}
 				proxy {
 					upstream redis:6379
-				}
+				}
 			}
 		}
 	}