fix: use valid Redis log levels and add log level comments to all containers

Redis only supports debug|verbose|notice|warning -- not info or error.
The command was using ${LOG_LEVEL:-info} which resolved to INFO in
production (from workflow env), causing Redis to crash loop. Hardcode
the correct Redis-native levels (debug for dev, warning for prod) and
add available log level comments above every container's log setting.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.prod.yml

@@ -12,9 +12,11 @@ services:
   # Traefik - Production log level and dashboard auth
   mvp-traefik:
     environment:
+      # Traefik log levels: TRACE | DEBUG | INFO | WARN | ERROR
       LOG_LEVEL: error
     command:
       - --configFile=/etc/traefik/traefik.yml
+      # Traefik log levels: TRACE | DEBUG | INFO | WARN | ERROR
       - --log.level=ERROR
     labels:
       - "traefik.enable=true"
@@ -30,6 +32,7 @@ services:
       NODE_ENV: production
       CONFIG_PATH: /app/config/production.yml
       SECRETS_DIR: /run/secrets
+      # Pino log levels: trace | debug | info | warn | error | fatal
       LOG_LEVEL: error
       DATABASE_HOST: mvp-postgres
       REDIS_HOST: mvp-redis
@@ -41,6 +44,7 @@ services:
   # OCR - Production log level + engine config
   mvp-ocr:
     environment:
+      # Python log levels: DEBUG | INFO | WARNING | ERROR | CRITICAL
       LOG_LEVEL: error
       REDIS_HOST: mvp-redis
       REDIS_PORT: 6379
@@ -59,13 +63,14 @@ services:
       POSTGRES_PASSWORD_FILE: /run/secrets/postgres-password
       POSTGRES_INITDB_ARGS: --encoding=UTF8
       LOG_LEVEL: error
+      # PostgreSQL log statements: none | ddl | mod | all
       POSTGRES_LOG_STATEMENT: none
+      # Minimum query duration to log: -1 (disabled) | 0 (all) | N (ms threshold)
       POSTGRES_LOG_MIN_DURATION_STATEMENT: -1
       PGDATA: /var/lib/postgresql/data/pgdata
 
   # Redis - Remove dev ports, production log level
   mvp-redis:
     ports: []
-    command: redis-server --appendonly yes --loglevel ${LOG_LEVEL:-info}
-    environment:
-      LOG_LEVEL: error
+    # Redis log levels: debug | verbose | notice | warning
+    command: redis-server --appendonly yes --loglevel warning