Pr/develop to 5fa3703 fix: multiple bug fixes, security hardening, Docker improvements and MCP enhancements

[wchy1128]

Summary

• Security hardening: AST sandbox escape remediation (CVSS 9.8), removed eval() from computed fields
• Docker: custom Dockerfile/patch build scripts, playground2 preview page, listen on all addresses, LLM table
  extraction allowlist
• MCP: ask endpoint schema fixes, browser/crawler config support across all endpoints
• Bug fixes: mermaid SVG text preservation ([Bug]: Missing Mermaid Flowcharts #1043), preserve .tail text ([Bug]: remove_empty_elements_fast() drops trailing text when removing empty elements with non-empty .tail #1938), deep-crawl ContextVar ([Bug]: Deep crawling crashes from time to time #1917),
  rowspan/colspan preservation, NlpSentenceChunking sentence order, semaphore_count wiring (Internal MemoryAdaptiveDispatcher ignores max_session_permit #1927), JS challenge HTTP
  status update, Bedrock provider prefix, arun() return type ([Bug]: arun() and arun_many() type hinting needs fixing #1898), Chinese output escaping
• Docs: Privacy Policy, Terms of Service, Support pages; arun() docstring update
• Features: arun_many config-list support in Docker API (Enhance Docker API to expose full arun_many config-list support #1837)

Test plan

• Verify Docker build and playground pages work
• Confirm MCP endpoints handle browser/crawler configs correctly
• Run regression test suite (c4ai-check passed)