feat(api): add webhook CRUD API router and tests (#393)

* 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>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Henry <30578846+hjball@users.noreply.github.com>

packages/api/src/root.ts

@@ -11,6 +11,7 @@ import { listRouter } from "./routers/list";
 import { memberRouter } from "./routers/member";
 import { permissionRouter } from "./routers/permission";
 import { userRouter } from "./routers/user";
+import { webhookRouter } from "./routers/webhook";
 import { workspaceRouter } from "./routers/workspace";
 import { createTRPCRouter } from "./trpc";
 
@@ -27,6 +28,7 @@ export const appRouter = createTRPCRouter({
   import: importRouter,
   permission: permissionRouter,
   user: userRouter,
+  webhook: webhookRouter,
   workspace: workspaceRouter,
   integration: integrationRouter,
 });