feat(admin): DB CRUD panel + /api/admin endpoints (#38)

- ADMIN button in the mission-control header opens a table picker + row grid with add/edit/delete (components/admin-panel.tsx), deliberately unauthenticated by explicit request
- /api/admin/tables and /api/admin/tables/{name}/rows driven off a name→table registry built from lib/db/schema.ts (lib/db/admin.ts) — no per-table code; 404 unknown table, 400 malformed payload, 409 constraint violation
- OpenAPI spec updated for all four admin operations + Admin* schemas
- unit: lib/db/admin.test.ts (registry, CRUD round-trips, composite PKs, error mapping); e2e: read-only admin.spec.ts

lib/openapi.test.ts

@@ -5,6 +5,8 @@ import { openApiSpec } from './openapi';
 describe('OpenAPI spec', () => {
   it('documents every public endpoint', () => {
     expect(Object.keys(openApiSpec.paths).sort()).toEqual([
+      '/api/admin/tables',
+      '/api/admin/tables/{name}/rows',
       '/api/crew',
       '/api/events',
       '/api/explore',