perf: reduce portable build size ~40MB — replace winsdk/wmi, migrate cv2 to Pillow

- Replace winsdk (~35MB) with winrt packages (~2.5MB) for OS notification
  listener. API is identical, 93% size reduction.
- Replace wmi (~3-5MB) with ctypes for monitor names (EnumDisplayDevicesW)
  and camera names (SetupAPI). Zero external dependency.
- Migrate cv2.resize/imencode/LUT to Pillow/numpy in 5 files (filters,
  preview helpers, kc_target_processor). OpenCV only needed for camera
  and video stream now.
- Fix DefWindowProcW ctypes overflow on 64-bit Python (pre-existing bug
  in platform_detector display power listener).
- Fix openLightbox import in streams-capture-templates.ts (was using
  broken window cast instead of direct import).
- Add mandatory data migration policy to CLAUDE.md after silent data
  loss incident from storage file rename without migration.

server/src/wled_controller/api/routes/_preview_helpers.py

@@ -43,15 +43,14 @@ def _encode_jpeg(pil_image: Image.Image, quality: int = 85) -> str:
 
 def encode_preview_frame(image: np.ndarray, max_width: int = None, quality: int = 80) -> bytes:
     """Encode a numpy RGB image to JPEG bytes, optionally downscaling."""
-    import cv2
+    pil_img = Image.fromarray(image)
     if max_width and image.shape[1] > max_width:
         scale = max_width / image.shape[1]
         new_h = int(image.shape[0] * scale)
-        image = cv2.resize(image, (max_width, new_h), interpolation=cv2.INTER_AREA)
-    # RGB -> BGR for OpenCV JPEG encoding
-    bgr = cv2.cvtColor(image, cv2.COLOR_RGB2BGR)
-    _, buf = cv2.imencode('.jpg', bgr, [cv2.IMWRITE_JPEG_QUALITY, quality])
-    return buf.tobytes()
+        pil_img = pil_img.resize((max_width, new_h), Image.LANCZOS)
+    buf = io.BytesIO()
+    pil_img.save(buf, format="JPEG", quality=quality)
+    return buf.getvalue()
 
 
 def _make_thumbnail(pil_image: Image.Image, max_width: int) -> Image.Image: