feat: add Postgres MCP integration for database testing

- Add postgres-mcp service to docker-compose.yml (SSE mode on port 8000)
- Add .mcp.json.example with SSE configuration template
- Add .gitignore entries for .claude/settings.local.json and .mcp.json
- Add MCP_EXAMPLES.md with query examples for testing scraping results
- Add analysis scripts: analyze-category-nulls.ts, check-product-details.ts,
  inspect-api-response.ts

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

.gitignore

@@ -35,3 +35,6 @@ test-results/
 playwright-report/
 playwright/.cache/
 
+# Claude Code
+.claude/settings.local.json
+.mcp.json