feat: implement real-time LED strip preview

- Add LED strip visualization around display previews
- Show real-time color status for each LED pixel
- Support multi-display LED strip configurations
- Use elegant 16px thin LED strip design
- Real-time LED color sync via WebSocket
- Responsive layout with display scaling support

src-tauri/capabilities/default.json

@@ -0,0 +1,10 @@
+{
+  "$schema": "../gen/schemas/desktop-schema.json",
+  "identifier": "default",
+  "description": "Capability for the main application window",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "shell:allow-open"
+  ]
+}