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>

tests/Unit/DatabaseTest.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace Tests\Unit;
+
+use PHPUnit\Framework\TestCase;
+use App\Database;
+use PDO;
+
+class DatabaseTest extends TestCase
+{
+    public function testGetInstanceReturnsPDO(): void
+    {
+        $db = Database::getInstance();
+        $this->assertInstanceOf(PDO::class, $db);
+    }
+
+    public function testGetInstanceReturnsSameInstance(): void
+    {
+        $db1 = Database::getInstance();
+        $db2 = Database::getInstance();
+        $this->assertSame($db1, $db2);
+    }
+
+    public function testDatabaseConnectionHasCorrectAttributes(): void
+    {
+        $db = Database::getInstance();
+
+        // Test error mode
+        $this->assertEquals(
+            PDO::ERRMODE_EXCEPTION,
+            $db->getAttribute(PDO::ATTR_ERRMODE)
+        );
+
+        // Test fetch mode
+        $this->assertEquals(
+            PDO::FETCH_ASSOC,
+            $db->getAttribute(PDO::ATTR_DEFAULT_FETCH_MODE)
+        );
+    }
+
+    public function testCanExecuteQuery(): void
+    {
+        $db = Database::getInstance();
+        $stmt = $db->query('SELECT 1 as test');
+        $result = $stmt->fetch();
+
+        $this->assertEquals(['test' => 1], $result);
+    }
+
+    public function testCanPrepareStatement(): void
+    {
+        $db = Database::getInstance();
+        $stmt = $db->prepare('SELECT ? as test');
+
+        $this->assertInstanceOf(\PDOStatement::class, $stmt);
+    }
+}