Add descriptive error messages across all API routes and toast notifications on client pages

- 86 catch blocks in 49 API route files now return the actual error message via error.message
- 14 campaign/lead/config catch blocks that lacked console.error now log errors
- 17 client pages/components now show toast.error notifications on API failures
- Silent .catch(() => {}) and finally-only try blocks now surface errors to users

src/app/api/event-users/route.ts

@@ -28,6 +28,7 @@ export async function GET() {
     return NextResponse.json({ users })
   } catch (error) {
     console.error("Event users error:", error)
-    return NextResponse.json({ error: "Failed to load users" }, { status: 500 })
+    const message = error instanceof Error ? error.message : "Failed to load users"
+    return NextResponse.json({ error: message }, { status: 500 })
   }
 }