docs: consolidate root documentation to README-* structure

- Created README-documentor.md: comprehensive guide for content contributors
- Created README-likec4.md: architecture modeling guide (merged from README-ARCHITECTURE.md + LIKEC4-QUICKSTART.md)
- Enhanced README-developer.md:
  - Added Docker/Container Build section (from DOCKER.md)
  - Expanded Testing section (from TESTING.md)
  - Added Version Management section (from VERSIONS.md)
  - Added LikeC4 tasks reference
- Updated README.md: modernized with badges and clear structure
- Deleted redundant files:
  - DOCUMENTOR-GUIDE.md (ASCII art, redundant to README-documentor.md)
  - DOCKER.md (integrated into README-developer.md)
  - TESTING.md (integrated into README-developer.md)
  - README-ARCHITECTURE.md (merged into README-likec4.md)
  - LIKEC4-QUICKSTART.md (merged into README-likec4.md)
  - VERSIONS.md (integrated into README-developer.md)
- Added devbox shell step to local-development.md

All hands-on documentation now follows README-* naming convention.
RELEASE.md retained as process documentation (not hands-on guide).

content/en/docs/documentation/local-development.md

@@ -31,6 +31,14 @@ Before you start, ensure you have:
    task deps:install
    ```
 
+3. **If using Devbox**, enter the Devbox shell:
+
+   ```bash
+   devbox shell
+   ```
+   
+   This ensures all tools (Hugo, Node.js, Go) are available in the correct versions.
+
 ## Local Development Workflow
 
 {{< likec4-view view="localDevelopment" project="documentation-platform" >}}