Add PHPUnit tests and update UI

- Add PHPUnit 11.0 testing framework
- Create unit tests for Database and Crawler classes
- Create integration tests for Crawler
- Add phpunit.xml configuration
- Change UI background color to rose
- All 9 tests passing

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

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

src/index.php

@@ -13,7 +13,7 @@
 
         body {
             font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
-            background: #f5f7fa;
+            background: #ffe4e9;
             padding: 20px;
         }