feat: add background sync for Matrix client on mobile platforms

- Introduced background sync functionality for the Matrix client, allowing notifications to be received even when the app is backgrounded.
- Added new commands to start, stop, and get the state of background sync.
- Implemented a BackgroundSyncManager to manage sync state and credentials.
- Integrated matrix-sdk for handling Matrix interactions and notifications.
- Updated Cargo.toml to include necessary dependencies for background sync.
- Modified mobile capabilities to include opener permissions.
- Enhanced lib.rs to handle new commands and integrate background sync logic.

src-tauri/gen/schemas/capabilities.json

@@ -1 +1 @@
-{"default":{"identifier":"default","description":"Default capability for all windows","local":true,"windows":["*"],"permissions":["core:default","opener:default","opener:allow-open-url","opener:allow-default-urls","notification:default","autostart:default"],"platforms":["linux","windows","macOS"]},"mobile":{"identifier":"mobile","description":"Default capability for mobile","local":true,"windows":["*"],"permissions":["core:default","notification:default","deep-link:default"],"platforms":["android","iOS"]}}
+{"default":{"identifier":"default","description":"Default capability for all windows","local":true,"windows":["*"],"permissions":["core:default","opener:default","opener:allow-open-url","opener:allow-default-urls","notification:default","autostart:default"],"platforms":["linux","windows","macOS"]},"mobile":{"identifier":"mobile","description":"Default capability for mobile","local":true,"windows":["*"],"permissions":["core:default","notification:default","deep-link:default","opener:default"],"platforms":["android","iOS"]}}