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/routes/system.py

@@ -0,0 +1,93 @@
+"""System routes: health, version, displays."""
+
+import sys
+from datetime import datetime
+
+from fastapi import APIRouter, HTTPException
+
+from wled_controller import __version__
+from wled_controller.api.auth import AuthRequired
+from wled_controller.api.schemas.system import (
+    DisplayInfo,
+    DisplayListResponse,
+    HealthResponse,
+    VersionResponse,
+)
+from wled_controller.core.screen_capture import get_available_displays
+from wled_controller.utils import get_logger
+
+logger = get_logger(__name__)
+
+router = APIRouter()
+
+
+@router.get("/health", response_model=HealthResponse, tags=["Health"])
+async def health_check():
+    """Check service health status.
+
+    Returns basic health information including status, version, and timestamp.
+    """
+    logger.info("Health check requested")
+
+    return HealthResponse(
+        status="healthy",
+        timestamp=datetime.utcnow(),
+        version=__version__,
+    )
+
+
+@router.get("/api/v1/version", response_model=VersionResponse, tags=["Info"])
+async def get_version():
+    """Get version information.
+
+    Returns application version, Python version, and API version.
+    """
+    logger.info("Version info requested")
+
+    return VersionResponse(
+        version=__version__,
+        python_version=f"{sys.version_info.major}.{sys.version_info.minor}.{sys.version_info.micro}",
+        api_version="v1",
+    )
+
+
+@router.get("/api/v1/config/displays", response_model=DisplayListResponse, tags=["Config"])
+async def get_displays(_: AuthRequired):
+    """Get list of available displays.
+
+    Returns information about all available monitors/displays that can be captured.
+    """
+    logger.info("Listing available displays")
+
+    try:
+        # Get available displays with all metadata (name, refresh rate, etc.)
+        display_dataclasses = get_available_displays()
+
+        # Convert dataclass DisplayInfo to Pydantic DisplayInfo
+        displays = [
+            DisplayInfo(
+                index=d.index,
+                name=d.name,
+                width=d.width,
+                height=d.height,
+                x=d.x,
+                y=d.y,
+                is_primary=d.is_primary,
+                refresh_rate=d.refresh_rate,
+            )
+            for d in display_dataclasses
+        ]
+
+        logger.info(f"Found {len(displays)} displays")
+
+        return DisplayListResponse(
+            displays=displays,
+            count=len(displays),
+        )
+
+    except Exception as e:
+        logger.error(f"Failed to get displays: {e}")
+        raise HTTPException(
+            status_code=500,
+            detail=f"Failed to retrieve display information: {str(e)}"
+        )