refactor: Webhooks (#12487)

Closes #12303

### What’s Changed
- Replace auto‐save with explicit Save / Cancel
Webhook forms now use manual “Save” and “Cancel” buttons instead of the
old debounced auto‐save/update.

- Separate “New” and “Detail” routes
Two dedicated paths `/settings/webhooks/new` for creation and
/`settings/webhooks/:webhookId` for editing, making the UX clearer.

- URL hint & normalization
If a user omits the http(s):// scheme, we display a “Will be saved as
https://…” hint and automatically default to HTTPS.

- Centralized validation with Zod
Introduced a `webhookFormSchema` for client‐side URL, operations, and
secret validation.

- Storybook coverage
Added stories for both “New Webhook” and “Webhook Detail”

- Unit tests
Added tests for the new `useWebhookForm` hook

packages/twenty-server/src/modules/webhook/query-hooks/webhook-url-validation.service.ts

@@ -0,0 +1,29 @@
+import { Injectable } from '@nestjs/common';
+
+import {
+  GraphqlQueryRunnerException,
+  GraphqlQueryRunnerExceptionCode,
+} from 'src/engine/api/graphql/graphql-query-runner/errors/graphql-query-runner.exception';
+
+@Injectable()
+export class WebhookUrlValidationService {
+  validateWebhookUrl(targetUrl: string): void {
+    let parsedUrl: URL;
+
+    try {
+      parsedUrl = new URL(targetUrl);
+    } catch {
+      throw new GraphqlQueryRunnerException(
+        `Invalid URL: missing scheme. URLs must include http:// or https://. Received: ${targetUrl}`,
+        GraphqlQueryRunnerExceptionCode.INVALID_QUERY_INPUT,
+      );
+    }
+
+    if (!['http:', 'https:'].includes(parsedUrl.protocol)) {
+      throw new GraphqlQueryRunnerException(
+        `Invalid URL scheme. Only HTTP and HTTPS are allowed. Received: ${parsedUrl.protocol}`,
+        GraphqlQueryRunnerExceptionCode.INVALID_QUERY_INPUT,
+      );
+    }
+  }
+}