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/src/wled_controller/core/wled_client.py

@@ -234,26 +234,35 @@ class WLEDClient:
         if not 0 <= brightness <= 255:
             raise ValueError(f"Brightness must be 0-255, got {brightness}")
 
-        # Validate pixel values
+        # Validate and convert pixel values to Python ints (handles numpy types)
+        # WLED expects a flat array: [r1, g1, b1, r2, g2, b2, ...]
+        flat_pixels = []
         for i, (r, g, b) in enumerate(pixels):
             if not (0 <= r <= 255 and 0 <= g <= 255 and 0 <= b <= 255):
                 raise ValueError(f"Invalid RGB values at index {i}: ({r}, {g}, {b})")
+            # Convert to Python int and flatten to [r, g, b, r, g, b, ...]
+            flat_pixels.extend([int(r), int(g), int(b)])
 
-        # Build WLED JSON state
+        # Build WLED JSON state with flat pixel array
         payload = {
             "on": True,
-            "bri": brightness,
+            "bri": int(brightness),  # Ensure brightness is also a Python int
             "seg": [
                 {
                     "id": segment_id,
-                    "i": pixels,  # Individual LED colors
+                    "i": flat_pixels,  # Individual LED colors as flat array
                 }
             ],
         }
 
+        # Log payload details for debugging
+        logger.debug(f"Sending {len(pixels)} LEDs ({len(flat_pixels)} values) to WLED")
+        logger.debug(f"Payload size: ~{len(str(payload))} bytes")
+        logger.debug(f"First 3 LEDs: {flat_pixels[:9] if len(flat_pixels) >= 9 else flat_pixels}")
+
         try:
             await self._request("POST", "/json/state", json_data=payload)
-            logger.debug(f"Sent {len(pixels)} pixel colors to WLED device")
+            logger.debug(f"Successfully sent pixel colors to WLED device")
             return True
 
         except Exception as e: