Add PWA support and mobile responsive layout

- PWA manifest, service worker (stale-while-revalidate for static assets,
  network-only for API), and app icons for installability
- Root-scoped /manifest.json and /sw.js routes in FastAPI
- New mobile.css with responsive breakpoints at 768/600/400px:
  fixed bottom tab bar on phones, single-column cards, full-screen modals,
  compact header toolbar, touch-friendly targets
- Fix modal-content-wide min-width overflow on small screens
- Update README with Camera, OpenRGB, and PWA features

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

README.md

@@ -13,7 +13,7 @@ A Home Assistant integration exposes devices as entities for smart home automati
 ### Screen Capture
 
 - Multi-monitor support with per-target display selection
-- 5 capture engine backends — MSS (cross-platform), DXCam, BetterCam, Windows Graphics Capture (Windows), Scrcpy (Android via ADB)
+- 6 capture engine backends — MSS (cross-platform), DXCam, BetterCam, Windows Graphics Capture (Windows), Scrcpy (Android via ADB), Camera/Webcam (OpenCV)
 - Configurable capture regions, FPS, and border width
 - Capture templates for reusable configurations
 
@@ -23,6 +23,7 @@ A Home Assistant integration exposes devices as entities for smart home automati
 - Adalight (serial) — Arduino-compatible LED controllers
 - AmbileD (serial)
 - DDP (Distributed Display Protocol, UDP)
+- OpenRGB — PC peripherals (keyboard, mouse, RAM, fans, LED strips)
 - Serial port auto-detection and baud rate configuration
 
 ### Color Processing
@@ -48,6 +49,8 @@ A Home Assistant integration exposes devices as entities for smart home automati
 ### Dashboard
 
 - Web UI at `http://localhost:8080` — no installation needed on the client side
+- Progressive Web App (PWA) — installable on phones and tablets with offline caching
+- Responsive mobile layout with bottom tab navigation
 - Device management with auto-discovery wizard
 - Visual calibration editor with overlay preview
 - Live LED strip preview via WebSocket
@@ -72,6 +75,7 @@ A Home Assistant integration exposes devices as entities for smart home automati
 | Feature | Windows | Linux / macOS |
 | ------- | ------- | ------------- |
 | Screen capture | DXCam, BetterCam, WGC, MSS | MSS |
+| Webcam capture | OpenCV (DirectShow) | OpenCV (V4L2) |
 | Audio capture | WASAPI, Sounddevice | Sounddevice (PulseAudio/PipeWire) |
 | GPU monitoring | NVIDIA (pynvml) | NVIDIA (pynvml) |
 | Android capture | Scrcpy (ADB) | Scrcpy (ADB) |
@@ -114,8 +118,8 @@ wled-screen-controller/
 │   │   │   └── schemas/             # Pydantic request/response models
 │   │   ├── core/
 │   │   │   ├── capture/             # Screen capture, calibration, pixel processing
-│   │   │   ├── capture_engines/     # MSS, DXCam, BetterCam, WGC, Scrcpy backends
-│   │   │   ├── devices/             # WLED, Adalight, AmbileD, DDP clients
+│   │   │   ├── capture_engines/     # MSS, DXCam, BetterCam, WGC, Scrcpy, Camera backends
+│   │   │   ├── devices/             # WLED, Adalight, AmbileD, DDP, OpenRGB clients
 │   │   │   ├── audio/               # Audio capture engines
 │   │   │   ├── filters/             # Post-processing filter pipeline
 │   │   │   ├── processing/          # Stream orchestration and target processors
@@ -214,10 +218,11 @@ black src/ tests/
 ruff check src/ tests/
 ```
 
-Optional high-performance capture engines (Windows only):
+Optional extras:
 
 ```bash
-pip install -e ".[perf]"
+pip install -e ".[perf]"     # High-performance capture engines (Windows)
+pip install -e ".[camera]"   # Webcam capture via OpenCV
 ```
 
 ## License