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/utils/webhook.ts

@@ -185,12 +185,13 @@ export async function sendWebhooksForWorkspace(
   payload: WebhookPayload,
 ): Promise<void> {
   try {
-    // Get active webhooks for this workspace
-    const webhooks = await webhookRepo.getActiveByWorkspaceId(db, workspaceId);
-
-    // Filter webhooks that are subscribed to this specific event
-    const webhooksForEvent = webhooks.filter((webhook) =>
-      webhook.events.includes(payload.event),
+    // Get active webhooks for this workspace and filter by event client-side
+    const allWebhooks = await webhookRepo.getActiveByWorkspaceId(
+      db,
+      workspaceId,
+    );
+    const webhooks = allWebhooks.filter((w) =>
+      w.events.includes(payload.event),
     );
 
     // Send to all subscribed webhooks in parallel (fire and forget)