test(api): add temporary pocketbase harness for api tests

`pnpm test:api` starts an isolated PocketBase with project migrations and
hooks in a temp dir, provides SDK client helpers and cleans up after the run,
on failure and on SIGINT/SIGTERM. The superuser is generated per instance.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EvmtStx737hu8gXe15e55W

vitest.api.config.ts

@@ -0,0 +1,11 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+    test: {
+        include: ['tests/api/**/*.api.spec.ts'],
+        globalSetup: ['tests/api/global-setup.ts'],
+        // Headroom for starting a temporary PocketBase inside a test.
+        testTimeout: 20_000,
+        hookTimeout: 20_000,
+    },
+});