docs: organize audits and add GPT-5.6 independent review

Reorganize audit documents into an audits/ subdirectory and add a comprehensive independent audit by GPT-5.6.

Changes:
- Renamed AUDIT.md → audits/DOCKIFY-AUDIT-GLM-5.2.md to clarify source
- Added audits/DOCKIFY-AUDIT-GPT-5.6-SOL.md with:
  - 23 detailed findings across security, correctness, reliability, and operations
  - Wave 0–3 prioritized roadmap with dependency analysis
  - Validation strategy and implementation sequencing
  - Final verdict: not suitable for production exposure until Wave 0/1 complete

The independent audit validates prior findings and surfaces new issues (basic-auth Caddy JSON mismatch, app worker migration, default Compose key persistence) while providing a structured recovery path for the product.

Author: coderbuzz