fix(grafana): reject invalid panels JSON instead of silently ignoring it

Grafana's dashboard API treats panels as a required array and returns 400 on
invalid JSON; this route already errors on every other JSON param. Return
'Invalid JSON for panels parameter' instead of swallowing the parse error and
proceeding with a misleading success.

Author: waleedlatif1

apps/sim/app/api/tools/grafana/update_dashboard/route.ts

@@ -116,7 +116,13 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
     if (params.panels) {
       try {
         updatedDashboard.panels = JSON.parse(params.panels)
-      } catch {}
+      } catch {
+        return NextResponse.json({
+          success: false,
+          output: {},
+          error: 'Invalid JSON for panels parameter',
+        })
+      }
     }
 
     if (existingDashboard.version) {