Add Playwright headless browser as 3rd crawling fallback

Crawl chain: Jsoup → Jina Reader → Playwright (headless Chromium).
Error page detection (403, Access Denied, etc.) triggers next fallback.
Switch to exploded classpath for Playwright driver-bundle compatibility.
Fix Next.js standalone static file serving with symlink.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

sundol-backend/pom.xml

@@ -104,6 +104,18 @@
             <version>1.18.3</version>
         </dependency>
 
+        <!-- Playwright (headless browser, driver-bundle includes node runtime) -->
+        <dependency>
+            <groupId>com.microsoft.playwright</groupId>
+            <artifactId>playwright</artifactId>
+            <version>1.51.0</version>
+        </dependency>
+        <dependency>
+            <groupId>com.microsoft.playwright</groupId>
+            <artifactId>driver-bundle</artifactId>
+            <version>1.51.0</version>
+        </dependency>
+
         <!-- Jackson -->
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>