Add Discord webhook notifications for bot restarts

Sends instant notifications to Discord when the bot restarts, helping
track stability issues and auto-recovery events.

Changes:
- Add notify_restart.py script to send webhook notifications
- Integrate notification into bot startup (on_ready event)

The notification includes:
- Timestamp of restart (CST)
- Reason (healthcheck failure detection)
- Reference to diagnostics logs

Configuration:
Set RESTART_WEBHOOK_URL environment variable in docker-compose.yml
to enable notifications.

This provides immediate visibility when Docker auto-restarts the bot
due to crashes or healthcheck failures.

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

notify_restart.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+"""
+Notify admin channel when bot restarts due to healthcheck failure.
+Uses Discord webhook for instant notification.
+"""
+
+import os
+import urllib.request
+import json
+from datetime import datetime
+
+
+def send_restart_notification():
+    """Send notification to Discord via webhook."""
+    webhook_url = os.getenv("RESTART_WEBHOOK_URL")
+
+    if not webhook_url:
+        print("No RESTART_WEBHOOK_URL configured, skipping notification")
+        return False
+
+    try:
+        timestamp = datetime.now().strftime("%Y-%m-%d %H:%M:%S CST")
+
+        data = {
+            "content": (
+                f"**Paper Dynasty Bot Auto-Restarted** at {timestamp}\n\n"
+                "Healthcheck detected bot was offline/frozen. "
+                "Bot has been automatically restarted.\n\n"
+                "Check `/logs/restart_diagnostics.log` for details."
+            ),
+            "username": "Paper Dynasty Monitor",
+        }
+
+        req = urllib.request.Request(
+            webhook_url,
+            data=json.dumps(data).encode("utf-8"),
+            headers={"Content-Type": "application/json"},
+        )
+
+        response = urllib.request.urlopen(req, timeout=5)
+
+        if response.status == 204:
+            print(f"Restart notification sent successfully at {timestamp}")
+            return True
+        else:
+            print(f"Webhook returned status {response.status}")
+            return False
+
+    except Exception as e:
+        print(f"Failed to send restart notification: {e}")
+        return False
+
+
+if __name__ == "__main__":
+    send_restart_notification()

paperdynasty.py

@@ -9,6 +9,7 @@ from discord.ext import commands
 
 from in_game.gameplay_models import create_db_and_tables
 from health_server import run_health_server
+from notify_restart import send_restart_notification
 
 raw_log_level = os.getenv('LOG_LEVEL')
 if raw_log_level == 'DEBUG':
@@ -70,6 +71,9 @@ async def on_ready():
     logger.info(bot.user.name)
     logger.info(bot.user.id)
 
+    # Send restart notification if configured
+    send_restart_notification()
+
 
 @bot.tree.error
 async def on_app_command_error(interaction: discord.Interaction, error: discord.app_commands.AppCommandError):