feat(organizations): email inviter when membership invite is accepted

When a user accepts an org invite, send a notification email to the
person who sent the invite with membership details (member name, email,
org name, role) and an optional View Organization button.

Added build_invite_accepted_html() template to email_templates.py,
wired it into the accept_invite() handler, and added a test case.

gatehouse_app/api/v1/organizations/invites.py

@@ -243,6 +243,30 @@ def accept_invite(token):
 
     invite.accept()
 
+    if invite.invited_by and invite.invited_by.email:
+        from gatehouse_app.services.email_templates import build_invite_accepted_html
+        from gatehouse_app.services.notification_service import NotificationService
+
+        member_display = user.full_name or user.email
+        inviter_display = invite.invited_by.full_name or invite.invited_by.email
+        org_link = f"{current_app.config.get('APP_URL', '')}/organizations/{invite.organization_id}"
+
+        html_body = build_invite_accepted_html(
+            inviter_name=inviter_display,
+            member_name=member_display,
+            member_email=user.email,
+            org_name=invite.organization.name,
+            role=invite.role,
+            org_link=org_link,
+        )
+
+        NotificationService._send_email_async(
+            to_address=invite.invited_by.email,
+            subject=f"{member_display} accepted your invitation to {invite.organization.name}",
+            body=f"{member_display} has accepted your invitation to join {invite.organization.name} on Secuird.",
+            html_body=html_body,
+        )
+
     has_webauthn = user.has_webauthn_enabled()
     has_totp = user.has_totp_enabled()
 

gatehouse_app/services/email_templates.py

@@ -562,3 +562,51 @@ def build_contact_enquiry_html(
     <p style="margin: 0; color: {TEXT_COLOR}; font-size: 14px; line-height: 1.6; white-space: pre-wrap;">{message_display}</p>
     '''
     return get_base_html(content, f"Secuird Website: {type_label}", f"New {type_label} from {submitter_email}")
+
+
+def build_invite_accepted_html(
+    inviter_name: str,
+    member_name: str,
+    member_email: str,
+    org_name: str,
+    role: str,
+    org_link: Optional[str] = None,
+) -> str:
+    """Build invite accepted notification email.
+
+    Args:
+        inviter_name: Name of the person who sent the invite
+        member_name: Name of the person who accepted
+        member_email: Email of the person who accepted
+        org_name: Organization name
+        role: Role assigned to the member
+        org_link: Optional link to view the organization
+
+    Returns:
+        HTML email string
+    """
+    content = f'''
+    <h2 style="margin: 0 0 20px 0; color: {TEXT_COLOR}; font-size: 20px; font-weight: 600;">Invitation Accepted</h2>
+    <p style="margin: 0 0 20px 0; color: {TEXT_COLOR}; font-size: 15px; line-height: 1.6;">
+        <strong>{member_name}</strong> has accepted your invitation to join <strong>{org_name}</strong> on Secuird.
+    </p>
+    {get_alert_box(f"<strong>{member_name}</strong> ({member_email}) has joined <strong>{org_name}</strong>", "success", "✅")}
+    <table role="presentation" width="100%" cellspacing="0" cellpadding="0" style="margin: 20px 0; background-color: {BACKGROUND_COLOR}; border-radius: 8px;">
+        <tr>
+            <td style="padding: 20px;">
+                <h3 style="margin: 0 0 16px 0; color: {TEXT_COLOR}; font-size: 14px; font-weight: 600;">Membership Details</h3>
+                <table role="presentation" width="100%" cellspacing="0" cellpadding="0">
+                    {get_detail_row("Member", member_name)}
+                    {get_detail_row("Email", member_email)}
+                    {get_detail_row("Organization", org_name)}
+                    {get_detail_row("Role", role)}
+                </table>
+            </td>
+        </tr>
+    </table>
+    '''
+    if org_link:
+        content += get_action_button(org_link, "View Organization", PRIMARY_COLOR)
+
+    return get_base_html(content, f"Invitation accepted: {org_name}", f"{member_name} has joined {org_name}")
+

test_email.py

@@ -148,8 +148,28 @@ def test_html_email():
         success = provider.send(message)
         print(f"Result: {'✅ SUCCESS' if success else '❌ FAILED'}")
 
+        # Test 8: Invite Accepted
+        print("\n--- Test 8: Invite Accepted ---")
+        html_body = email_templates.build_invite_accepted_html(
+            inviter_name="Admin User",
+            member_name="New Member",
+            member_email="newmember@example.com",
+            org_name="Acme Corporation",
+            role="Member",
+            org_link="https://secuird.tech/organizations/org-123",
+        )
+        message = EmailMessage(
+            to="cory@hawkvelt.id.au",
+            subject="New Member accepted your invitation to Acme Corporation",
+            body="Plain text version: New Member has accepted your invitation.",
+            html_body=html_body,
+            from_address="Secuird <noreply@secuird.tech>",
+        )
+        success = provider.send(message)
+        print(f"Result: {'✅ SUCCESS' if success else '❌ FAILED'}")
+
         print("\n" + "=" * 50)
-        print("All 7 email templates sent!")
+        print("All 8 email templates sent!")
         print("=" * 50)