feat: module architecture improvements — session keys, dependency graph, event dispatcher, deactivation hooks

Six targeted improvements to the modular monolith platform:

1. Fix AddressBook session key prefix to follow module.<id>.* convention
2. Move ADDRESS_BOOK_VIEW permission constant from core PermissionService into module
3. Add declarative JSON schema for module manifests (.agents/contracts/)
4. Add `requires` field with missing-dependency and circular-dependency detection
5. Add lightweight fire-and-forget event dispatcher (user.created/deleted/login/logout)
6. Add module deactivation hook interface and CLI script (bin/module-deactivate.php)

Includes 15 new architecture/unit tests covering all new functionality.

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

tests/Unit/Module/LayoutContextProviderTest.php

@@ -38,7 +38,7 @@ final class LayoutContextProviderTest extends TestCase
         $container = new AppContainer();
 
         $session = [
-            'available_departments_by_tenant' => [
+            'module.addressbook.departments_by_tenant' => [
                 [
                     'tenant' => ['uuid' => 'abc', 'description' => 'Tenant A'],
                     'departments' => [['id' => 1, 'description' => 'Dept 1']],