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>

api/database/migrations/2026_04_07_250000_fix_organisations_and_invitations.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        // Fix billing_status default from 'active' to 'trial'
+        Schema::table('organisations', function (Blueprint $table) {
+            $table->string('billing_status')->default('trial')->change();
+        });
+
+        // Fix invited_by_user_id: nullOnDelete instead of cascadeOnDelete
+        Schema::table('user_invitations', function (Blueprint $table) {
+            $table->dropForeign(['invited_by_user_id']);
+            $table->foreignUlid('invited_by_user_id')->nullable()->change();
+            $table->foreign('invited_by_user_id')->references('id')->on('users')->nullOnDelete();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('organisations', function (Blueprint $table) {
+            $table->string('billing_status')->default('active')->change();
+        });
+
+        Schema::table('user_invitations', function (Blueprint $table) {
+            $table->dropForeign(['invited_by_user_id']);
+            $table->foreignUlid('invited_by_user_id')->change();
+            $table->foreign('invited_by_user_id')->references('id')->on('users')->cascadeOnDelete();
+        });
+    }
+};