feat(web): add webhook management UI (#394)

* feat(api): add webhook CRUD API router and tests

Add tRPC router for managing workspace webhooks:

- list, create, update, delete endpoints (admin role required)
- test endpoint to send a synthetic payload to a webhook URL
- URL validation, event subscription filtering
- Unit tests for all router procedures
- Integration tests with PGlite test database
- Add vitest config and test infrastructure for API package

Depends on #391 (DB schema & repository).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor(api): use assertPermission instead of assertUserInWorkspace

Replace assertUserInWorkspace with assertPermission("workspace:manage")
per project conventions. The permissions system is the preferred
authorization approach for new code.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(api): use @kan/db alias instead of relative imports in tests

Replace relative path imports (../../db/src/...) with the @kan/db
alias configured in vitest.config.ts for consistency and robustness.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor(api): use webhookUrlSchema in router input validation

Cherry-pick router-related changes from b2cc9ac:
- Use extracted webhookUrlSchema zod validator in create/update
  input schemas for consistent SSRF checks

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor(api): replace dynamic import with static import for webhook utility

Add packages/api/src/utils/webhook.ts with sendWebhookToUrl,
createCardWebhookPayload, and webhookUrlSchema. Replace the dynamic
import() in the test endpoint with a static import at the top of the
file for better tree-shaking, type-checking, and readability.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(api): align sendWebhooksForWorkspace tests with merged PR #392

The merged delivery utility uses client-side event filtering
(getActiveByWorkspaceId takes 2 args, not 3). Update test assertions
to match the actual implementation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat(web): add webhook management UI

Add settings page for managing workspace webhooks:

- Add webhooks page route and settings navigation link
- Add webhook list view with status toggles and action menus
- Add create/edit modal with URL validation and event selection
- Add delete confirmation dialog
- Add WEBHOOKS_ENABLED env flag for feature gating

Depends on #393 (CRUD API router).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(web): remove dead env vars, extract TableRow, import webhookEvents

- Remove unused WEBHOOK_URL and WEBHOOK_SECRET env vars (leftovers
  from earlier env-var-based design)
- Move TableRow component outside WebhookList to avoid re-creation
  on every render
- Import webhookEvents from @kan/db/schema instead of hardcoding
- Simplify formatDate to only handle Date objects (strings are not
  returned by tRPC/Superjson)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(web): gate webhooks settings tab to admin role

The webhook API requires admin role, but the settings tab was visible
to all users (condition: true). Now matches the API's authorization
requirement, addressing reviewer feedback on PR #394.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor(web): use webhookEvents constant for form defaults

Replace hardcoded event arrays with [...webhookEvents] in
NewWebhookModal so default values stay in sync if new events
are added to the schema.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(web): use date-fns with locale for webhook date formatting

Replace hardcoded toLocaleDateString('en-US') with date-fns format()
using the useLocalisation() hook's dateLocale, matching the pattern
used throughout the codebase (ActivityList, DateSelector, etc.).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/pages/settings/webhooks.tsx

@@ -0,0 +1,16 @@
+import type { NextPageWithLayout } from "~/pages/_app";
+import { getDashboardLayout } from "~/components/Dashboard";
+import { SettingsLayout } from "~/components/SettingsLayout";
+import WebhookSettings from "~/views/settings/WebhookSettings";
+
+const WebhookSettingsPage: NextPageWithLayout = () => {
+  return (
+    <SettingsLayout currentTab="webhooks">
+      <WebhookSettings />
+    </SettingsLayout>
+  );
+};
+
+WebhookSettingsPage.getLayout = (page) => getDashboardLayout(page);
+
+export default WebhookSettingsPage;