feat: extract bookmarks as standalone module with MintyPHP\Module\Bookmarks namespace

Moves bookmarks from core hardcoding into modules/bookmarks/ as a
fully self-contained module, following the same pattern as addressbook.

Module contributions via platform slots:
- aside.tab_panel: bookmark sidebar panel
- topbar.right_item: bookmark toggle button
- layout.body_end_template: bookmark/group dialogs
- layout.head_style: bookmark CSS (form + sidebar)
- runtime.component: bookmark-save and bookmark-panel (phase: late)
- search.resource_item: bookmarks in global search (user-scoped via {{userId}})

Backend fully in module namespace (MintyPHP\Module\Bookmarks\*):
- Service: BookmarkService, BookmarkServicesFactory, BookmarkRepositoryFactory
- Repository: BookmarkRepository, BookmarkGroupRepository, BookmarkNavigationRepository
- Support: BookmarkUrlNormalizer
- Providers: BookmarksSessionProvider, BookmarksLayoutProvider, BookmarksSearchProvider

Core cleanup:
- Removed all bookmark-specific markup from core templates
- Removed core DI registrations for bookmark services
- Removed core bookmark pages, JS, CSS
- AuthSessionTenantContextService delegates to module SessionProvider

Architecture guards:
- NoBookmarksHardcodingTest: verifies zero bookmark references in core
- testModuleClassesUseModuleNamespace: prevents core namespace leakage

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

modules/bookmarks/pages/bookmarks/group-delete-data().php

@@ -0,0 +1,48 @@
+<?php
+
+use MintyPHP\Http\SessionStoreInterface;
+use MintyPHP\Router;
+use MintyPHP\Module\Bookmarks\Service\BookmarkService;
+use MintyPHP\Session;
+use MintyPHP\Support\Guard;
+
+Guard::requireLogin();
+
+if (requestInput()->method() !== 'POST') {
+    http_response_code(405);
+    Router::json(['ok' => false, 'error' => 'method_not_allowed']);
+    return;
+}
+
+if (!Session::checkCsrfToken()) {
+    http_response_code(403);
+    Router::json(['ok' => false, 'error' => 'csrf']);
+    return;
+}
+
+$session = app(SessionStoreInterface::class)->all();
+$userId = (int) ($session['user']['id'] ?? 0);
+if ($userId <= 0) {
+    http_response_code(401);
+    Router::json(['ok' => false, 'error' => 'unauthorized']);
+    return;
+}
+
+$groupId = (int) requestInput()->body('id');
+if ($groupId <= 0) {
+    http_response_code(400);
+    Router::json(['ok' => false, 'error' => 'invalid_group_id']);
+    return;
+}
+
+$service = app(BookmarkService::class);
+$deleted = $service->deleteGroup($userId, $groupId);
+
+if ($deleted) {
+    app(SessionStoreInterface::class)->set('module.bookmarks.grouped', $service->listGroupedForUser($userId));
+    Router::json(['ok' => true]);
+    return;
+}
+
+http_response_code(404);
+Router::json(['ok' => false, 'error' => 'not_found']);