Add invite request system and Gitea Actions CI/CD pipeline

Invite request feature:
- Public form to request an invite when INVITE_REQUEST_ENABLED=true
- Stores requests in new invite_requests DB table
- Emails admins on new request, emails requester on approve/deny
- Admin panel tab to review, approve, and deny requests
- Approval auto-creates invite code and sends signup link

CI/CD pipeline:
- Build & push Docker image to Gitea registry on release
- Auto-deploy to staging with health check
- Manual workflow_dispatch for production deploys

Also includes client layout/sizing improvements for card grid
and opponent spacing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/services/email_service.py

@@ -165,6 +165,76 @@ class EmailService:
 
         return await self._send_email(to, subject, html)
 
+    async def send_invite_request_admin_notification(
+        self,
+        to: str,
+        requester_name: str,
+        requester_email: str,
+        message: str,
+    ) -> Optional[str]:
+        """Notify admin of a new invite request."""
+        if not self.is_configured():
+            logger.info(f"Email not configured. Would send invite request notification to {to}")
+            return None
+
+        admin_url = f"{self.base_url}/admin.html"
+        message_html = f"<p><strong>Message:</strong> {message}</p>" if message else ""
+
+        subject = f"Golf Game invite request from {requester_name}"
+        html = f"""
+        <h2>New Invite Request</h2>
+        <p><strong>Name:</strong> {requester_name}</p>
+        <p><strong>Email:</strong> {requester_email}</p>
+        {message_html}
+        <p><a href="{admin_url}">Review in Admin Panel</a></p>
+        """
+
+        return await self._send_email(to, subject, html)
+
+    async def send_invite_approved_email(
+        self,
+        to: str,
+        name: str,
+        invite_code: str,
+    ) -> Optional[str]:
+        """Notify requester that their invite was approved."""
+        if not self.is_configured():
+            logger.info(f"Email not configured. Would send invite approval to {to}")
+            return None
+
+        signup_url = f"{self.base_url}/?invite={invite_code}"
+
+        subject = "Your Golf Game invite is ready!"
+        html = f"""
+        <h2>You're In, {name}!</h2>
+        <p>Your request to join Golf Game has been approved.</p>
+        <p>Use this link to create your account:</p>
+        <p><a href="{signup_url}">{signup_url}</a></p>
+        <p>Or sign up manually with invite code: <strong>{invite_code}</strong></p>
+        <p>This invite is single-use and expires in 7 days.</p>
+        """
+
+        return await self._send_email(to, subject, html)
+
+    async def send_invite_denied_email(
+        self,
+        to: str,
+        name: str,
+    ) -> Optional[str]:
+        """Notify requester that their invite was denied."""
+        if not self.is_configured():
+            logger.info(f"Email not configured. Would send invite denial to {to}")
+            return None
+
+        subject = "Golf Game invite request update"
+        html = f"""
+        <h2>Hi {name},</h2>
+        <p>Thanks for your interest in Golf Game. Unfortunately, we're not able to approve your invite request at this time.</p>
+        <p>We may open up registrations in the future — stay tuned!</p>
+        """
+
+        return await self._send_email(to, subject, html)
+
     async def _send_email(
         self,
         to: str,