Implement ID-based routing and folder auto-generation from titles

Major features:
- Switch from slug-based to ID-based routing (/documents/123)
- Enable title editing with automatic slug/path regeneration
- Auto-generate folder structure from title slashes (e.g., Laravel/Livewire/Components)
- Persist sidebar folder open/close state using localStorage
- Remove slug unique constraint (ID routing makes it unnecessary)
- Implement recursive tree view with multi-level folder support

Architecture changes:
- DocumentService: Add generatePathAndSlug() for title-based path generation
- Routes: Change from {document:slug} to {document} for ID binding
- SidebarTree: Extract recursive rendering to partials/tree-item.blade.php
- Database: Remove unique constraint from documents.slug column

UI improvements:
- Display only last path component in sidebar (Components vs Laravel/Livewire/Components)
- Folder state persists across page navigation via localStorage
- Title field accepts slashes for folder organization

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/resources/views/livewire/sidebar-tree.blade.php

@@ -0,0 +1,31 @@
+<div class="p-4" x-data="sidebarState()" x-init="initExpandedFolders()">
+    <div class="mb-4">
+        <h2 class="text-sm font-semibold text-gray-700 uppercase tracking-wider">
+            Documents
+        </h2>
+    </div>
+
+    @if(empty($tree))
+        <div class="text-sm text-gray-500 italic">
+            No documents found
+        </div>
+    @else
+        <div class="space-y-1">
+            @include('partials.tree-item', ['tree' => $tree, 'path' => ''])
+        </div>
+    @endif
+
+    @auth
+        <div class="mt-6 pt-6 border-t border-gray-200">
+            <a
+                href="{{ route('documents.create') }}"
+                class="flex items-center justify-center px-4 py-2 text-sm font-medium text-white bg-indigo-600 rounded-md hover:bg-indigo-700"
+            >
+                <svg class="w-4 h-4 mr-2" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 4v16m8-8H4"></path>
+                </svg>
+                New Document
+            </a>
+        </div>
+    @endauth
+</div>