Implement email alert system with WhatsApp notifications

- Added alerts processing logic in src/alerts.py to analyze threads and send WhatsApp alerts based on configured time frames.
- Created FastAPI application in src/app.py to manage threads, display configurations, and trigger alert processing.
- Developed database models and utility functions in src/database.py for managing threads and messages.
- Integrated Twilio API for sending WhatsApp messages in src/whatsapp_sender.py.
- Implemented Zoho email client in src/zoho_client.py to fetch emails and check for replies.
- Added configuration management for email settings and alert parameters.
- Established auto-processing loop for periodic email syncing and alert generation.

templates/config.html

@@ -47,6 +47,15 @@
       </div>
     </div>
 
+    <h3 class="mt-2">WhatsApp</h3>
+    <div class="row">
+      <div class="col">
+        <label>Send To (WhatsApp E.164, no spaces)<br>
+          <input type="text" name="whatsapp_to" placeholder="+15551234567" value="{{ cfg.whatsapp_to or '' }}" />
+        </label>
+      </div>
+    </div>
+
     <h3 class="mt-2">Processing</h3>
     <div class="row">
       <div class="col">