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>

lib/App/Module/Contracts/ModuleDeactivationHandler.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace MintyPHP\App\Module\Contracts;
+
+use MintyPHP\App\AppContainer;
+
+/**
+ * Handles cleanup when a module is deactivated.
+ *
+ * Invoked by `bin/module-deactivate.php` after a module has been removed
+ * from the enabled list. The handler receives the full app container and
+ * can perform cleanup tasks like removing orphaned data or revoking permissions.
+ */
+interface ModuleDeactivationHandler
+{
+    public function deactivate(AppContainer $container): void;
+}