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/lib/Module/Bookmarks/Repository/BookmarkNavigationRepositoryInterface.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace MintyPHP\Module\Bookmarks\Repository;
+
+interface BookmarkNavigationRepositoryInterface
+{
+    public function nextRootSortOrder(int $userId): int;
+
+    /** @param list<array{kind: 'group'|'bookmark', id: int, sort_order: int}> $rootOrderPairs */
+    public function updateRootSortOrders(int $userId, array $rootOrderPairs): bool;
+}