feat: migrate from Electron to Tauri v2

This is a complete migration of Gitify from Electron to Tauri v2.

Changes include:
- Remove Electron main/preload processes and webpack configs
- Add Tauri v2 backend with Rust (src-tauri/)
- Add Vite bundler configuration
- Migrate renderer code from src/renderer/ to src/
- Migrate tests from Jest to Vitest
- Update all dependencies for Tauri compatibility
- Add type-safe context hook (useAppContext)
- Fix strict TypeScript mode issues

BREAKING CHANGE: This replaces the Electron backend with Tauri.

Author: afonsojramos

.env.example

@@ -0,0 +1,6 @@
+# GitHub OAuth Application Credentials
+# Create an OAuth app at https://github.com/settings/developers
+# Set the callback URL to: gitify://auth-callback
+
+OAUTH_CLIENT_ID=your_github_oauth_client_id
+OAUTH_CLIENT_SECRET=your_github_oauth_client_secret

babel.config.js

@@ -1,8 +1,5 @@
 {
-  "$schema": "https://biomejs.dev/schemas/2.3.10/schema.json",
-  "files": {
-    "includes": ["**", "!**/generated/**/*"]
-  },
+  "$schema": "https://biomejs.dev/schemas/2.3.5/schema.json",
   "assist": {
     "actions": {
       "source": {