Add Gmail and Google Calendar integration

Implements on-demand Google tools (not adapter) for email and calendar access via OAuth2.

Features:
- OAuth2 user consent flow with automatic token refresh
- 3 Gmail tools: send_email, read_emails, get_email
- 3 Calendar tools: read_calendar, create_calendar_event, search_calendar
- Lazy loading pattern for Google clients
- Secure token storage with file permissions
- Browser-based setup: python bot_runner.py --setup-google

Architecture:
- Tools-only approach (zero API calls when not in use)
- User-initiated actions only (no continuous polling)
- MIME message creation for emails with threading support
- HTML to text conversion for email parsing
- ISO 8601 timestamp handling for calendar events

Files added:
- google_tools/oauth_manager.py: OAuth2 flow and token management
- google_tools/gmail_client.py: Gmail API wrapper
- google_tools/calendar_client.py: Calendar API wrapper
- google_tools/utils.py: Email/MIME helpers
- config/scheduled_tasks.yaml: Example scheduled tasks config

Files modified:
- tools.py: Added 6 Google tool handlers with lazy initialization
- bot_runner.py: Added --setup-google command for OAuth authorization
- requirements.txt: Added Google API dependencies
- .gitignore: Added google_credentials.yaml and google_oauth_token.json

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

bot_runner.py

@@ -26,6 +26,7 @@ from adapters.slack.adapter import SlackAdapter
 from adapters.telegram.adapter import TelegramAdapter
 from agent import Agent
 from config.config_loader import ConfigLoader
+from google_tools.oauth_manager import GoogleOAuthManager
 from scheduled_tasks import TaskScheduler
 
 # Adapter class registry mapping platform names to their classes
@@ -195,6 +196,16 @@ def main() -> None:
         action="store_true",
         help="Run health check",
     )
+    parser.add_argument(
+        "--setup-google",
+        action="store_true",
+        help="Set up Google OAuth for Gmail/Calendar integration",
+    )
+    parser.add_argument(
+        "--manual",
+        action="store_true",
+        help="Use manual OAuth code entry (for headless servers)",
+    )
 
     args = parser.parse_args()
 
@@ -209,6 +220,32 @@ def main() -> None:
         print("3. Run: python bot_runner.py")
         return
 
+    if args.setup_google:
+        print("=" * 60)
+        print("Google OAuth Setup")
+        print("=" * 60)
+        print()
+        oauth_manager = GoogleOAuthManager()
+
+        if oauth_manager.is_authorized():
+            print("✓ Already authorized!")
+            print(f"✓ Tokens found at {oauth_manager.token_file}")
+            print("\nTo re-authorize, delete the token file and run this command again.")
+            return
+
+        success = oauth_manager.run_oauth_flow(manual=args.manual)
+        if success:
+            print("You can now use Gmail and Calendar tools!")
+            print("\nTest it:")
+            print("  Via Telegram: \"What's on my calendar?\"")
+            print("  Via Telegram: \"Send an email to john@example.com\"")
+        else:
+            print("\nSetup failed. Please check:")
+            print("1. config/google_credentials.yaml exists with valid client_id/client_secret")
+            print("2. You authorized the app in your browser")
+            print("3. No firewall blocking localhost:8080")
+        return
+
     runner = BotRunner(config_file=args.config)
 
     if args.health: