Organize planning documents and update README structure

- Created a new `docs/planning/` directory to better organize architecture and implementation planning documents.
- Moved existing planning documents into the new directory for improved accessibility.
- Updated `README.md` to reflect the new document structure and added references to the organized planning documents.
- Enhanced overall documentation management for easier navigation and maintenance.

README.md

@@ -45,7 +45,15 @@ igny8/
 │   ├── 04-BACKEND-IMPLEMENTATION.md
 │   ├── 05-AI-FRAMEWORK-IMPLEMENTATION.md
 │   ├── 06-FUNCTIONAL-BUSINESS-LOGIC.md
-│   └── API-COMPLETE-REFERENCE.md  # Complete unified API documentation
+│   ├── API-COMPLETE-REFERENCE.md  # Complete unified API documentation
+│   ├── planning/        # Architecture & implementation planning documents
+│   │   ├── IGNY8-HOLISTIC-ARCHITECTURE-PLAN.md  # Complete architecture plan
+│   │   ├── IGNY8-IMPLEMENTATION-PLAN.md  # Step-by-step implementation plan
+│   │   ├── Igny8-phase-2-plan.md  # Phase 2 feature specifications
+│   │   ├── CONTENT-WORKFLOW-DIAGRAM.md  # Content workflow diagrams
+│   │   ├── ARCHITECTURE_CONTEXT.md  # Architecture context reference
+│   │   └── sample-usage-limits-credit-system  # Credit system specification
+│   └── refactor/        # Refactoring plans and documentation
 ├── CHANGELOG.md         # Version history and changes (only updated after user confirmation)
 └── docker-compose.app.yml
 ```