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/phpunit.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+>
+    <testsuites>
+        <testsuite name="Unit">
+            <directory>tests/Unit</directory>
+        </testsuite>
+        <testsuite name="Feature">
+            <directory>tests/Feature</directory>
+        </testsuite>
+    </testsuites>
+    <source>
+        <include>
+            <directory>app</directory>
+        </include>
+    </source>
+    <php>
+        <env name="APP_ENV" value="testing"/>
+        <env name="APP_MAINTENANCE_DRIVER" value="file"/>
+        <env name="BCRYPT_ROUNDS" value="4"/>
+        <env name="BROADCAST_CONNECTION" value="null"/>
+        <env name="CACHE_STORE" value="array"/>
+        <env name="DB_CONNECTION" value="sqlite"/>
+        <env name="DB_DATABASE" value=":memory:"/>
+        <env name="MAIL_MAILER" value="array"/>
+        <env name="QUEUE_CONNECTION" value="sync"/>
+        <env name="SESSION_DRIVER" value="array"/>
+        <env name="PULSE_ENABLED" value="false"/>
+        <env name="TELESCOPE_ENABLED" value="false"/>
+        <env name="NIGHTWATCH_ENABLED" value="false"/>
+    </php>
+</phpunit>