feat(org): add organization limit per user

Add 10 organization limit per user to prevent abuse. Includes
graceful fallback if count service is unavailable.

- Add get_user_org_count method to OrganizationService
- Check org count before allowing new organization creation
- Improve invite email mismatch error message for logged-in users

gatehouse_app/api/v1/organizations/core.py

@@ -1,4 +1,5 @@
 """Organization core CRUD endpoints."""
+import logging
 from flask import g, request
 from marshmallow import ValidationError
 from gatehouse_app.api.v1 import api_v1_bp
@@ -12,6 +13,15 @@ from gatehouse_app.services.organization_service import OrganizationService
 @login_required
 @full_access_required
 def create_organization():
+    try:
+        org_count = OrganizationService.get_user_org_count(g.current_user.id)
+        if org_count is not None and org_count >= 10:
+            return api_response(success=False, message="You cannot belong to more than 10 organizations", status=400, error_type="ORG_LIMIT_REACHED")
+    except Exception as e:
+        logger = logging.getLogger(__name__)
+        logger.warning(f"[Org] Failed to check org count for user {g.current_user.id}: {e}")
+        # Fail open to avoid blocking legitimate users when the count service is unavailable
+
     try:
         schema = OrganizationCreateSchema()
         data = schema.load(request.json)

gatehouse_app/api/v1/organizations/invites.py

@@ -173,7 +173,7 @@ def accept_invite(token):
             if session_user.email.lower() != invite.email.lower():
                 return api_response(
                     success=False,
-                    message="This invite was sent to a different email address.",
+                    message="You are already logged in and this invite was sent to a different email address.",
                     status=403,
                     error_type="EMAIL_MISMATCH",
                 )

gatehouse_app/services/organization_service.py

@@ -70,6 +70,22 @@ class OrganizationService:
 
         return org
 
+    @staticmethod
+    def get_user_org_count(user_id):
+        """
+        Get the count of organizations a user belongs to.
+
+        Args:
+            user_id: User ID
+
+        Returns:
+            Count of active memberships (deleted_at is NULL)
+        """
+        return OrganizationMember.query.filter_by(
+            user_id=user_id,
+            deleted_at=None,
+        ).count()
+
     @staticmethod
     def get_organization_by_id(org_id):
         """