Refactor capture engine architecture, rename PictureStream to PictureSource, and split API modules

- Separate CaptureEngine into stateless factory + stateful CaptureStream session
- Add LiveStream/LiveStreamManager for shared capture with reference counting
- Rename PictureStream to PictureSource across storage, API, and UI
- Remove legacy migration logic and unused compatibility code
- Split monolithic routes.py (1935 lines) into 5 focused route modules
- Split schemas.py (480 lines) into 7 schema modules with re-exports
- Extract dependency injection into dedicated dependencies.py

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

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

@@ -0,0 +1,75 @@
+"""Capture template and engine schemas."""
+
+from datetime import datetime
+from typing import Dict, List, Optional
+
+from pydantic import BaseModel, Field
+
+
+class TemplateCreate(BaseModel):
+    """Request to create a capture template."""
+
+    name: str = Field(description="Template name", min_length=1, max_length=100)
+    engine_type: str = Field(description="Engine type (e.g., 'mss', 'dxcam', 'wgc')", min_length=1)
+    engine_config: Dict = Field(default_factory=dict, description="Engine-specific configuration")
+    description: Optional[str] = Field(None, description="Template description", max_length=500)
+
+
+class TemplateUpdate(BaseModel):
+    """Request to update a template."""
+
+    name: Optional[str] = Field(None, description="Template name", min_length=1, max_length=100)
+    engine_type: Optional[str] = Field(None, description="Capture engine type (mss, dxcam, wgc)")
+    engine_config: Optional[Dict] = Field(None, description="Engine-specific configuration")
+    description: Optional[str] = Field(None, description="Template description", max_length=500)
+
+
+class TemplateResponse(BaseModel):
+    """Template information response."""
+
+    id: str = Field(description="Template ID")
+    name: str = Field(description="Template name")
+    engine_type: str = Field(description="Engine type identifier")
+    engine_config: Dict = Field(description="Engine-specific configuration")
+    created_at: datetime = Field(description="Creation timestamp")
+    updated_at: datetime = Field(description="Last update timestamp")
+    description: Optional[str] = Field(None, description="Template description")
+
+
+class TemplateListResponse(BaseModel):
+    """List of templates response."""
+
+    templates: List[TemplateResponse] = Field(description="List of templates")
+    count: int = Field(description="Number of templates")
+
+
+class EngineInfo(BaseModel):
+    """Capture engine information."""
+
+    type: str = Field(description="Engine type identifier (e.g., 'mss', 'dxcam')")
+    name: str = Field(description="Human-readable engine name")
+    default_config: Dict = Field(description="Default configuration for this engine")
+    available: bool = Field(description="Whether engine is available on this system")
+
+
+class EngineListResponse(BaseModel):
+    """List of available engines response."""
+
+    engines: List[EngineInfo] = Field(description="Available capture engines")
+    count: int = Field(description="Number of engines")
+
+
+class TemplateAssignment(BaseModel):
+    """Request to assign template to device."""
+
+    template_id: str = Field(description="Template ID to assign")
+
+
+class TemplateTestRequest(BaseModel):
+    """Request to test a capture template."""
+
+    engine_type: str = Field(description="Capture engine type to test")
+    engine_config: Dict = Field(default={}, description="Engine configuration")
+    display_index: int = Field(description="Display index to capture")
+    border_width: int = Field(default=10, ge=1, le=100, description="Border width in pixels")
+    capture_duration: float = Field(default=5.0, ge=1.0, le=30.0, description="Duration to capture in seconds")