feat: Windows-native desktop polish (tray, single-instance, deep links, Mica, installer)

- System tray with Open/Quit menu + left-click toggle; closing the window now
  minimizes to tray instead of quitting, so notifications keep arriving.
- Single-instance: a second launch focuses the running window (and forwards a
  matrix: link) instead of colliding on the localhost port.
- Window: 1100x720 default, 480x600 min, centered first run; starts hidden and
  shows on page-load to kill the white launch flash (8s failsafe).
- matrix: deep links via tauri-plugin-deep-link -> dispatched to the web client
  (useDeepLinkNavigate) for both cold-start and already-running cases.
- Windows 11 Mica backdrop (subtle; app paints opaque TDS bg).
- NSIS installer: per-user install (no UAC), downloadBootstrapper.
- Remove dead/broken src/menu.rs.
- Bump cinny submodule to 053b364a (deep-link web handler).

Note: Rust not compiled locally (no toolchain / Windows-only paths); verified by
careful API review against tauri 2.10 — needs a real 'tauri build' to confirm.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src-tauri/Cargo.toml

@@ -29,6 +29,7 @@ tauri-plugin-process = "2"
 tauri-plugin-os = "2"
 tauri-plugin-dialog = "2"
 tauri-plugin-opener = "2"
+tauri-plugin-deep-link = "2"
 
 [features]
 # by default Tauri runs in production mode
@@ -41,9 +42,11 @@ custom-protocol = [ "tauri/custom-protocol" ]
 [target.'cfg(not(any(target_os = "android", target_os = "ios")))'.dependencies]
 tauri-plugin-global-shortcut = "2"
 tauri-plugin-updater = "2"
+tauri-plugin-single-instance = "2"
 
 [target.'cfg(target_os = "windows")'.dependencies]
 webview2-com = "0.38"
+window-vibrancy = "0.6"
 windows = { version = "0.61", features = [
     "Win32_Graphics_Gdi",
     "Win32_System_Com",