feat: Implement OAuth2 authentication with Google and GitHub

- Added OAuth2 endpoints for Google and GitHub authentication.
- Created OAuth service to handle provider interactions and user info retrieval.
- Implemented user OAuth repository for managing user OAuth links in the database.
- Updated auth service to support linking existing users and creating new users via OAuth.
- Added CORS middleware to allow frontend access.
- Created tests for OAuth endpoints and service functionality.
- Introduced environment configuration for OAuth client IDs and secrets.
- Added logging for OAuth operations and error handling.

.env.template

@@ -0,0 +1,29 @@
+# Application Configuration
+HOST=localhost
+PORT=8000
+RELOAD=true
+
+# Database Configuration
+DATABASE_URL=sqlite+aiosqlite:///data/soundboard.db
+DATABASE_ECHO=false
+
+# Logging Configuration
+LOG_LEVEL=info
+LOG_FILE=logs/app.log
+LOG_MAX_SIZE=10485760
+LOG_BACKUP_COUNT=5
+
+# JWT Configuration
+JWT_SECRET_KEY=your-secret-key-change-in-production
+JWT_ACCESS_TOKEN_EXPIRE_MINUTES=15
+JWT_REFRESH_TOKEN_EXPIRE_DAYS=7
+
+# Cookie Configuration
+COOKIE_SECURE=false
+
+# OAuth2 Configuration
+GOOGLE_CLIENT_ID=
+GOOGLE_CLIENT_SECRET=
+GITHUB_CLIENT_ID=
+GITHUB_CLIENT_SECRET=
+OAUTH_REDIRECT_URL=http://localhost:8001/auth/callback