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>

.env.example

@@ -13,7 +13,7 @@ MC_SERIAL_PORT=/dev/serial/by-id/usb-Espressif_Systems_heltec_wifi_lora_32_v4__1
 MC_DEVICE_NAME=MarWoj
 
 # MeshCore configuration directory (where .msgs file is stored)
-MC_CONFIG_DIR=/root/.config/meshcore
+MC_CONFIG_DIR=/home/marek/.config/meshcore
 
 # ============================================
 # Application Settings
@@ -30,7 +30,7 @@ MC_INACTIVE_HOURS=48
 # ============================================
 
 # Directory for storing archived messages
-MC_ARCHIVE_DIR=/mnt/archive/meshcore
+MC_ARCHIVE_DIR=/home/marek/.config/meshcore/archive
 
 # Enable automatic daily archiving at midnight
 MC_ARCHIVE_ENABLED=true
@@ -50,3 +50,11 @@ FLASK_PORT=5000
 
 # Debug mode (true/false) - use false in production
 FLASK_DEBUG=false
+
+# ============================================
+# System Configuration
+# ============================================
+
+# Timezone for container logs (default: UTC)
+# Examples: Europe/Warsaw, America/New_York, Asia/Tokyo
+TZ=Europe/Warsaw