feat: Add increment/decrement endpoints for CF account domain count

- Add POST /internal/{id}/increment endpoint
- Add POST /internal/{id}/decrement endpoint
- Prevent negative domain counts
- Return updated counts and available capacity
- Require internal API key authentication

backend/app/routes/cf_accounts.py

@@ -254,3 +254,91 @@ def get_cf_account_internal(account_id):
             'error': str(e)
         }), 500
 
+
+@cf_accounts_bp.route('/internal/<int:account_id>/increment', methods=['POST'])
+@internal_api_required
+def increment_domain_count_internal(account_id):
+    """
+    Internal API endpoint to increment domain count
+    Called when Customer Panel creates a domain using this CF account
+    Requires X-Internal-API-Key header
+    """
+    try:
+        account = CloudflareAccount.query.get(account_id)
+        if not account:
+            return jsonify({
+                'status': 'error',
+                'error': 'Account not found'
+            }), 404
+
+        if not account.is_active:
+            return jsonify({
+                'status': 'error',
+                'error': 'Account is not active'
+            }), 400
+
+        # Check capacity
+        if account.current_domains >= account.max_domains:
+            return jsonify({
+                'status': 'error',
+                'error': f'Account is full ({account.current_domains}/{account.max_domains})'
+            }), 400
+
+        # Increment domain count
+        old_count = account.current_domains
+        account.current_domains += 1
+        db.session.commit()
+
+        return jsonify({
+            'status': 'success',
+            'message': 'Domain count incremented',
+            'account_id': account.id,
+            'old_count': old_count,
+            'new_count': account.current_domains,
+            'available_capacity': account.max_domains - account.current_domains
+        }), 200
+
+    except Exception as e:
+        db.session.rollback()
+        return jsonify({
+            'status': 'error',
+            'error': str(e)
+        }), 500
+
+
+@cf_accounts_bp.route('/internal/<int:account_id>/decrement', methods=['POST'])
+@internal_api_required
+def decrement_domain_count_internal(account_id):
+    """
+    Internal API endpoint to decrement domain count
+    Called when Customer Panel deletes a domain using this CF account
+    Requires X-Internal-API-Key header
+    """
+    try:
+        account = CloudflareAccount.query.get(account_id)
+        if not account:
+            return jsonify({
+                'status': 'error',
+                'error': 'Account not found'
+            }), 404
+
+        # Decrement domain count (prevent negative)
+        old_count = account.current_domains
+        account.current_domains = max(0, account.current_domains - 1)
+        db.session.commit()
+
+        return jsonify({
+            'status': 'success',
+            'message': 'Domain count decremented',
+            'account_id': account.id,
+            'old_count': old_count,
+            'new_count': account.current_domains,
+            'available_capacity': account.max_domains - account.current_domains
+        }), 200
+
+    except Exception as e:
+        db.session.rollback()
+        return jsonify({
+            'status': 'error',
+            'error': str(e)
+        }), 500