feat: enhance abra installation with proper verification and user commands

- Replace incorrect file-based abra verification with functional testing
- Add network connectivity monitoring to abra installer service
- Implement retry logic with proper error handling
- Add user-friendly 'install' command for manual abra repair
- Update documentation to include install command and troubleshooting
- Fix false positive detection in abra installation verification

The enhanced service now:
- Uses 'sudo abra --version' for reliable verification
- Waits for internet connectivity before attempting installation
- Retries up to 3 times with proper backoff
- Provides clear success/failure reporting
- Includes automatic service restart on failure

User can now run 'install' command as fallback when abra installation fails.

docs/USB_BOOT_INSTRUCTIONS.md

@@ -78,6 +78,9 @@ setup
 # See available app recipes
 recipes
 
+# If abra installation failed (rare case)
+install
+
 # Get help
 help
 ```
@@ -120,3 +123,7 @@ Name: Android, Password: (ask facilitator)
 → WiFi should connect automatically to "CODE_CRISPIES"
 → If not, use mobile hotspot as backup
 → Check: nmcli connection show --active
+
+**Abra not working**
+→ Run: install
+→ Check: sudo systemctl status workshop-abra-install