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>

.gitignore

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+# 環境変数
+.env
+
+# Docker関連
+docker/mysql/data/
+
+# Laravel関連（srcフォルダ配下に作成される予定）
+src/vendor/
+src/node_modules/
+src/.env
+src/storage/*.key
+src/storage/logs/
+src/storage/framework/cache/
+src/storage/framework/sessions/
+src/storage/framework/views/
+src/bootstrap/cache/*
+
+# IDE関連
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS関連
+.DS_Store
+Thumbs.db