Replace HAOS light entity with select entities, add zero-brightness optimization

- Remove light.py platform (static color control via HA light entity)
- Add select.py with CSS Source and Brightness Source dropdowns for LED targets
- Coordinator now fetches color-strip-sources and value-sources lists
- Add generic update_target() method for partial target updates
- Clean up stale device registry entries on integration reload
- Skip frame sends when effective brightness is ~0 (suppresses unnecessary
  UDP/HTTP traffic while LEDs are dark)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/core/processing/wled_target_processor.py

@@ -577,6 +577,16 @@ class WledTargetProcessor(TargetProcessor):
 
                         cur_brightness = _effective_brightness(device_info)
 
+                        # Zero-brightness suppression: if output is black and
+                        # the last sent frame was also black, skip sending.
+                        if cur_brightness <= 1 and _prev_brightness <= 1 and has_any_frame:
+                            self._metrics.frames_skipped += 1
+                            while send_timestamps and send_timestamps[0] < loop_start - 1.0:
+                                send_timestamps.popleft()
+                            self._metrics.fps_current = len(send_timestamps)
+                            await asyncio.sleep(SKIP_REPOLL)
+                            continue
+
                         if frame is prev_frame_ref and cur_brightness == _prev_brightness:
                             # Same frame + same brightness — keepalive or skip
                             if self._needs_keepalive and has_any_frame and (loop_start - last_send_time) >= keepalive_interval: