Add Key Colors target type for extracting colors from screen regions

Introduce a new "key_colors" target type alongside WLED targets, enabling
real-time color extraction from configurable screen rectangles with
average/median/dominant modes, temporal smoothing, and WebSocket streaming.

- Split WledPictureTarget into its own module, add KeyColorsPictureTarget
- Add KC target lifecycle to ProcessorManager (register, start/stop, processing loop)
- Extend API routes and schemas for KC targets (CRUD, settings, state, metrics, colors)
- Add WebSocket endpoint for real-time color updates with auth
- Add KC sub-tab in Targets UI with editor modal and live color swatches
- Add EN and RU translations for all key colors strings

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

server/src/wled_controller/api/schemas/picture_targets.py

@@ -35,14 +35,51 @@ class ProcessingSettings(BaseModel):
     )
 
 
+class KeyColorRectangleSchema(BaseModel):
+    """A named rectangle for key color extraction (relative coords 0.0-1.0)."""
+
+    name: str = Field(description="Rectangle name", min_length=1, max_length=50)
+    x: float = Field(default=0.0, description="Left edge (0.0-1.0)", ge=0.0, le=1.0)
+    y: float = Field(default=0.0, description="Top edge (0.0-1.0)", ge=0.0, le=1.0)
+    width: float = Field(default=1.0, description="Width (0.0-1.0)", gt=0.0, le=1.0)
+    height: float = Field(default=1.0, description="Height (0.0-1.0)", gt=0.0, le=1.0)
+
+
+class KeyColorsSettingsSchema(BaseModel):
+    """Settings for key colors extraction."""
+
+    fps: int = Field(default=10, description="Extraction rate (1-60)", ge=1, le=60)
+    interpolation_mode: str = Field(default="average", description="Color mode (average, median, dominant)")
+    smoothing: float = Field(default=0.3, description="Temporal smoothing (0.0-1.0)", ge=0.0, le=1.0)
+    rectangles: List[KeyColorRectangleSchema] = Field(default_factory=list, description="Rectangles to extract colors from")
+
+
+class ExtractedColorResponse(BaseModel):
+    """A single extracted color."""
+
+    r: int = Field(description="Red (0-255)")
+    g: int = Field(description="Green (0-255)")
+    b: int = Field(description="Blue (0-255)")
+    hex: str = Field(description="Hex color (#rrggbb)")
+
+
+class KeyColorsResponse(BaseModel):
+    """Extracted key colors for a target."""
+
+    target_id: str = Field(description="Target ID")
+    colors: Dict[str, ExtractedColorResponse] = Field(description="Rectangle name -> color")
+    timestamp: Optional[datetime] = Field(None, description="Extraction timestamp")
+
+
 class PictureTargetCreate(BaseModel):
     """Request to create a picture target."""
 
     name: str = Field(description="Target name", min_length=1, max_length=100)
-    target_type: str = Field(default="wled", description="Target type (wled)")
+    target_type: str = Field(default="wled", description="Target type (wled, key_colors)")
     device_id: str = Field(default="", description="WLED device ID")
     picture_source_id: str = Field(default="", description="Picture source ID")
-    settings: Optional[ProcessingSettings] = Field(None, description="Processing settings")
+    settings: Optional[ProcessingSettings] = Field(None, description="Processing settings (for wled targets)")
+    key_colors_settings: Optional[KeyColorsSettingsSchema] = Field(None, description="Key colors settings (for key_colors targets)")
     description: Optional[str] = Field(None, description="Optional description", max_length=500)
 
 
@@ -52,7 +89,8 @@ class PictureTargetUpdate(BaseModel):
     name: Optional[str] = Field(None, description="Target name", min_length=1, max_length=100)
     device_id: Optional[str] = Field(None, description="WLED device ID")
     picture_source_id: Optional[str] = Field(None, description="Picture source ID")
-    settings: Optional[ProcessingSettings] = Field(None, description="Processing settings")
+    settings: Optional[ProcessingSettings] = Field(None, description="Processing settings (for wled targets)")
+    key_colors_settings: Optional[KeyColorsSettingsSchema] = Field(None, description="Key colors settings (for key_colors targets)")
     description: Optional[str] = Field(None, description="Optional description", max_length=500)
 
 
@@ -64,7 +102,8 @@ class PictureTargetResponse(BaseModel):
     target_type: str = Field(description="Target type")
     device_id: str = Field(default="", description="WLED device ID")
     picture_source_id: str = Field(default="", description="Picture source ID")
-    settings: ProcessingSettings = Field(description="Processing settings")
+    settings: Optional[ProcessingSettings] = Field(None, description="Processing settings (wled)")
+    key_colors_settings: Optional[KeyColorsSettingsSchema] = Field(None, description="Key colors settings (key_colors)")
     description: Optional[str] = Field(None, description="Description")
     created_at: datetime = Field(description="Creation timestamp")
     updated_at: datetime = Field(description="Last update timestamp")
@@ -81,11 +120,11 @@ class TargetProcessingState(BaseModel):
     """Processing state for a picture target."""
 
     target_id: str = Field(description="Target ID")
-    device_id: str = Field(description="Device ID")
+    device_id: Optional[str] = Field(None, description="Device ID")
     processing: bool = Field(description="Whether processing is active")
     fps_actual: Optional[float] = Field(None, description="Actual FPS achieved")
-    fps_target: int = Field(description="Target FPS")
-    display_index: int = Field(description="Current display index")
+    fps_target: int = Field(default=0, description="Target FPS")
+    display_index: int = Field(default=0, description="Current display index")
     last_update: Optional[datetime] = Field(None, description="Last successful update")
     errors: List[str] = Field(default_factory=list, description="Recent errors")
     wled_online: bool = Field(default=False, description="Whether WLED device is reachable")
@@ -103,7 +142,7 @@ class TargetMetricsResponse(BaseModel):
     """Target metrics response."""
 
     target_id: str = Field(description="Target ID")
-    device_id: str = Field(description="Device ID")
+    device_id: Optional[str] = Field(None, description="Device ID")
     processing: bool = Field(description="Whether processing is active")
     fps_actual: Optional[float] = Field(None, description="Actual FPS")
     fps_target: int = Field(description="Target FPS")