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/auth/login/route.ts

@@ -141,8 +141,9 @@ export async function POST(request: NextRequest) {
     return response
   } catch (error) {
     console.error("Login error:", error)
+    const message = error instanceof Error ? error.message : "Authentication service unavailable."
     return NextResponse.json(
-      { error: "Authentication service unavailable." },
+      { error: message },
       { status: 503 }
     )
   }