Add target FPS slider to Capture Settings and remove unused HACS workflow

- Add Target FPS slider (range 10-90) to Capture Settings dialog
- Fix settings PUT to merge with current values instead of resetting defaults
- Update FPS validation range to 10-90 in schema and config
- Remove irrelevant .github/workflows/validate.yml (HACS leftover)

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

server/src/wled_controller/config.py

@@ -28,8 +28,8 @@ class ProcessingConfig(BaseSettings):
     """Processing configuration."""
 
     default_fps: int = 30
-    max_fps: int = 60
-    min_fps: int = 1
+    max_fps: int = 90
+    min_fps: int = 10
     border_width: int = 10
     interpolation_mode: Literal["average", "median", "dominant"] = "average"