Add Sourcify Database page to Contract dataset section

Adds a new MDX file that imports content from the existing Database page
in "Sourcify in depth", making it accessible from both sidebar sections
without duplicating content.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: kuzdogan

docs/4. Contract dataset/5. Sourcify Database.mdx

@@ -0,0 +1,7 @@
+---
+slug: /contract-dataset/sourcify-database
+---
+
+import DatabaseContent from '../6. Sourcify in depth/3. Database.md';
+
+<DatabaseContent />