feat: extend module platform with UI slots, runtime components, CLI tooling and {{userId}} search support

Completes the generic module platform that enables modules to contribute
UI elements, runtime JS components, and search resources without any
core hardcoding.

New generic UI slot types:
- topbar.right_item: module-contributed topbar buttons
- layout.body_end_template: module-contributed dialog/overlay templates
- layout.head_style: module-contributed global CSS
- runtime.component: declarative JS component registration with phase ordering

New infrastructure:
- ModuleAutoloader: PSR-4 autoloading for module-local PHP classes
- ModuleRuntimePageBuilder: symlinks module pages into runtime directory
- ModuleRuntimeAssetPublisher: publishes module CSS/JS to web/modules/
- ModulePermissionSynchronizer: syncs module permissions to DB
- CLI scripts: module-runtime-sync, module-build, module-migrate,
  module-permissions-sync, module-assets-sync
- {{userId}} placeholder in SearchDataService for user-scoped search queries
- Component runtime with phased initialization (early/default/late)
- AppContainer.protectExistingBindings() to prevent module→core overwrites
- Architecture tests: ModuleStructureContractTest, CoreTemplateIsolationTest,
  FrontendComponentRuntimeContractTest, AppContainerIsolationContractTest

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

config/modules.php

@@ -4,10 +4,13 @@
  * Module activation configuration.
  *
  * Modules listed here are loaded at boot time. The APP_ENABLED_MODULES env
- * variable (comma-separated) overrides this list when set.
+ * variable controls overrides with deterministic semantics:
+ * - APP_ENABLED_MODULES not set: use this config list
+ * - APP_ENABLED_MODULES='': explicit no-modules mode
+ * - APP_ENABLED_MODULES='a,b': exact module list from env
  *
  * Each entry must match a directory name under modules/ containing a module.php manifest.
  */
 return [
-    'enabled_modules' => ['addressbook'],
+    'enabled_modules' => ['addressbook', 'bookmarks'],
 ];