fix(bridge): Replace polling with msg_subscribe for real-time messages

Critical fixes based on user feedback:

1. **Remove auto-recv polling (30s interval)**
   - Polling with 'recv' doesn't fetch NEW messages, only reads from .msgs
   - Wasteful - creates unnecessary command traffic

2. **Add msg_subscribe for real-time message reception**
   - meshcli's msg_subscribe enables automatic message events
   - Messages arrive via EventType.CHANNEL_MSG_RECV events
   - No polling needed - truly asynchronous

3. **Make TZ configurable via .env instead of hardcoded**
   - Changed docker-compose.yml: TZ=${TZ:-UTC}
   - Added TZ=Europe/Warsaw to .env.example
   - Users can now set their own timezone

4. **Remove unused shlex import**
   - Not needed after switching to manual double-quote wrapping

Technical details:
- msg_subscribe sends subscription command to meshcli at init
- meshcli then emits events when messages arrive
- Events trigger TTY errors (harmless - meshcli tries to print_above)
- Messages are still saved to .msgs file by meshcli core

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -14,7 +14,7 @@ services:
       - MC_SERIAL_PORT=${MC_SERIAL_PORT}
       - MC_CONFIG_DIR=/root/.config/meshcore
       - MC_DEVICE_NAME=${MC_DEVICE_NAME}
-      - TZ=Europe/Warsaw
+      - TZ=${TZ:-UTC}
     networks:
       - meshcore-net
     healthcheck:
@@ -48,7 +48,7 @@ services:
       - FLASK_HOST=${FLASK_HOST:-0.0.0.0}
       - FLASK_PORT=${FLASK_PORT:-5000}
       - FLASK_DEBUG=${FLASK_DEBUG:-false}
-      - TZ=Europe/Warsaw
+      - TZ=${TZ:-UTC}
     env_file:
       - .env
     depends_on: