Fix numpy serialization and add comprehensive error logging

Server fixes:
- Fix numpy uint8 JSON serialization by converting to Python int
- Change WLED payload to flat array format [r,g,b,r,g,b,...]
- Add payload debugging logs (size, LED count, sample data)

Web UI improvements:
- Add comprehensive console logging for device errors
- Log actual error messages from state.errors array
- Log device operations (start/stop/add) with details
- Fix password field form validation warning

The HTTP API may have payload size limitations for large LED counts.
Consider UDP protocols (DDP/E1.31) for better real-time performance.

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

server/CLAUDE.md

@@ -73,6 +73,10 @@ After restarting the server with new code:
 2. **Restart the server**
 3. Test with `GET /api/v1/config/displays`
 
+### Modifying server login:
+1. Update the logic.
+2. **Restart the server**
+
 ### Adding translations:
 1. Add keys to `static/locales/en.json` and `static/locales/ru.json`
 2. Add `data-i18n` attributes to HTML elements in `static/index.html`