- Renamed root INDEX.md to index.md (lowercase)
- Changed navigation title from "Documentation Index" to "Index"
- Removed caps lock for cleaner appearance
- Renamed subdirectory INDEX.md files to section-specific names:
- user/INDEX.md → user/user-guide.md
- developer/INDEX.md → developer/development.md
- operations/INDEX.md → operations/operations.md
- contributing/INDEX.md → contributing/contributing.md
- developer/api/INDEX.md → developer/api/api-reference.md
- developer/api/collections/INDEX.md → developer/api/collections/collections-api.md
- Updated all internal links to use new filenames
- Updated navigation.go to skip subdirectory INDEX files from sidebar
- Added Dockerfile to include docs directory in container build
This fixes the issue where multiple 'INDEX' links appeared in the sidebar,
making navigation confusing. Now each section has a descriptive name.