FRE-606: Add Tauri desktop framework with cross-platform support

- Configure Tauri v2 for macOS, Windows, Linux
- Implement native menu bar (File, Edit, View, Window, Help)
- Add system tray with show/hide/quit functionality
- Create auto-updater framework with periodic checks
- Set up window state persistence
- Configure plugins (fs, http, dialog, shell, store)
- Add build scripts for all platforms
- Include comprehensive documentation

Files:
- src-tauri/Cargo.toml
- src-tauri/tauri.conf.json
- src-tauri/build.rs
- src-tauri/src/main.rs
- src-tauri/src/lib.rs
- src-tauri/src/menu.rs
- src-tauri/src/tray.rs
- src-tauri/src/updater.rs
- src-tauri/Cargo.lock
- src-tauri/icons/tray-icon.svg
- src-tauri/tauri.build.conf
- src-tauri/README.md
- .gitignore
- package.json (Tauri CLI scripts)

src-tauri/tauri.conf.json

@@ -0,0 +1,98 @@
+{
+  "build": {
+    "beforeDevCommand": "npm run dev",
+    "beforeBuildCommand": "npm run build",
+    "devUrl": "http://localhost:5173",
+    "frontendDist": "../dist"
+  },
+  "bundle": {
+    "active": true,
+    "targets": "all",
+    "identifier": "com.frenocorp.app",
+    "icon": [
+      "icons/32x32.png",
+      "icons/128x128.png",
+      "icons/128x128@2x.png",
+      "icons/icon.icns",
+      "icons/icon.ico"
+    ],
+    "category": "Productivity",
+    "shortDescription": "FrenoCorp Desktop",
+    "longDescription": "Real-time collaboration software for screenwriters",
+    "resources": ["../README.md"],
+    "externalBin": [],
+    "copyright": "2026 FrenoCorp",
+    "license": "MIT",
+    "publisher": "FrenoCorp",
+    "deb": {
+      "depends": ["libgtk-3-0", "libwebkit2gtk-4.0"]
+    },
+    "macOS": {
+      "entitlements": null,
+      "exceptionDomain": "",
+      "frameworks": [],
+      "providerShortName": null,
+      "signingIdentity": null
+    },
+    "windows": {
+      "certificateThumbprint": null,
+      "digestAlgorithm": "sha256",
+      "timestampUrl": ""
+    }
+  },
+  "plugins": {
+    "fs": {
+      "allow": ["$APP/*", "$HOME/Documents/*"],
+      "requireLiteralLeadingDot": true
+    },
+    "store": {
+      "auto": true
+    }
+  },
+  "security": {
+    "csp": "default-src 'self'; img-src 'self' asset: https://asset.localhost",
+    "dangerousAllowNumericLiteralId": false
+  },
+  "systemTray": {
+    "iconPath": "icons/tray-icon.png",
+    "iconAsTemplate": true
+  },
+  "windows": [
+    {
+      "title": "FrenoCorp",
+      "width": 1280,
+      "height": 800,
+      "minWidth": 800,
+      "minHeight": 600,
+      "resizable": true,
+      "fullscreen": false,
+      "decorations": true,
+      "transparent": false,
+      "alwaysOnTop": false,
+      "visible": true,
+      "center": true,
+      "skipTaskbar": false
+    }
+  ],
+  "allowlist": {
+    "all": true,
+    "fs": {
+      "all": true,
+      "scope": ["$APP/*", "$HOME/Documents/FrenoCorp/*"]
+    },
+    "shell": {
+      "all": true,
+      "open": true
+    },
+    "dialog": {
+      "all": true,
+      "open": true,
+      "save": true
+    },
+    "http": {
+      "all": true,
+      "scope": ["http://*", "https://*"]
+    }
+  },
+  "macOSPrivateApi": true
+}