Add ADB-based Android screen capture engine with display picker integration

New scrcpy/ADB capture engine that captures Android device screens over
ADB using screencap polling. Supports USB and WiFi ADB connections with
device auto-discovery. Engine-aware display picker shows Android devices
when scrcpy engine is selected, with inline ADB connect form for WiFi
devices.

Key changes:
- New scrcpy_engine.py using adb screencap polling (~1-2 FPS over WiFi)
- Engine-aware GET /config/displays?engine_type= API
- ADB connect/disconnect API endpoints (POST /adb/connect, /adb/disconnect)
- Display picker supports engine-specific device lists
- Stream/test modals pass engine type to display picker
- Test template handler changed to sync def to prevent event loop blocking
- Restart script merges registry PATH for newly-installed tools
- All engines (including unavailable) shown in engine list with status flag

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

server/src/wled_controller/static/locales/en.json

@@ -37,6 +37,13 @@
   "displays.picker.title": "Select a Display",
   "displays.picker.select": "Select display...",
   "displays.picker.click_to_select": "Click to select this display",
+  "displays.picker.adb_connect": "Connect ADB device",
+  "displays.picker.adb_connect.placeholder": "IP address (e.g. 192.168.2.201)",
+  "displays.picker.adb_connect.button": "Connect",
+  "displays.picker.adb_connect.success": "Device connected",
+  "displays.picker.adb_connect.error": "Failed to connect device",
+  "displays.picker.adb_disconnect": "Disconnect",
+  "displays.picker.no_android": "No Android devices found. Connect via USB or enter IP above.",
   "templates.title": "\uD83D\uDCC4 Engine Templates",
   "templates.description": "Capture templates define how the screen is captured. Each template uses a specific capture engine (MSS, DXcam, WGC) with custom settings. Assign templates to devices for optimal performance.",
   "templates.loading": "Loading templates...",