feat: consolidate frontend API layer, add query-client, and harden backend Fase 1

Frontend:
- Consolidate duplicate API layers into single src/lib/axios.ts per app
- Remove src/lib/api-client.ts and src/utils/api.ts (admin)
- Add src/lib/query-client.ts with TanStack Query config per app
- Update all imports and auto-import config

Backend:
- Fix organisations.billing_status default to 'trial'
- Fix user_invitations.invited_by_user_id to nullOnDelete
- Add MeResource with separated app_roles and pivot-based org roles
- Add cross-org check to EventPolicy view() and update()
- Restrict EventPolicy create/update to org_admin/event_manager (not org_member)
- Attach creator as org_admin on organisation store
- Add query scopes to Event and UserInvitation models
- Improve factories with Dutch test data
- Expand test suite from 29 to 41 tests (90 assertions)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/app/src/lib/query-client.ts

@@ -0,0 +1,12 @@
+import type { VueQueryPluginOptions } from '@tanstack/vue-query'
+
+export const queryClientConfig: VueQueryPluginOptions = {
+  queryClientConfig: {
+    defaultOptions: {
+      queries: {
+        staleTime: 1000 * 60 * 5, // 5 minutes
+        retry: 1,
+      },
+    },
+  },
+}