refactor: standardize markdown file naming to kebab-case convention

Renamed all documentation files to follow kebab-case naming standard:
- UPPERCASE files → lowercase (e.g., RBAC.md → rbac.md)
- snake_case files → kebab-case (e.g., icons_guide.md → icons-guide.md)
- SCREAMING_SNAKE_CASE → kebab-case (e.g., DATABASE_SETUP_GUIDE.md → database-setup-guide.md)

Files renamed (15 total):
API Documentation:
  - api/RBAC.md → api/rbac.md

Architecture:
  - architecture/API_CONSOLIDATION_PROPOSAL.md → api-consolidation-proposal.md
  - architecture/API_MIGRATION_STATUS.md → api-migration-status.md

Development:
  - development/AUTH_DEPENDENCIES_GUIDE.md → auth-dependencies-guide.md
  - development/CUSTOMER_AUTHENTICATION_IMPLEMENTATION.md → customer-authentication-implementation.md
  - development/CUSTOMER_AUTH_SUMMARY.md → customer-auth-summary.md
  - development/icons_guide.md → icons-guide.md

Database Seeder:
  - database-seeder/DATABASE_INIT_GUIDE.md → database-init-guide.md
  - database-seeder/DATABASE_QUICK_REFERENCE_GUIDE.md → database-quick-reference-guide.md
  - database-seeder/DATABASE_SEEDER_DOCUMENTATION.md → database-seeder-documentation.md
  - database-seeder/MAKEFILE_DATABASE_SEEDER.md → makefile-database-seeder.md

Error Rendering:
  - error-rendering/ERROR_RENDERING_DEVELOPER_DOCUMENTATION.md → error-rendering-developer-documentation.md
  - error-rendering/HTML_ERROR_RENDERING_FLOW_DIAGRAM.md → html-error-rendering-flow-diagram.md

Getting Started:
  - getting-started/DATABASE_QUICK_REFERENCE.md → database-quick-reference.md
  - getting-started/DATABASE_SETUP_GUIDE.md → database-setup-guide.md

Updates:
- Updated all references in mkdocs.yml
- Updated all cross-references in markdown files
- Verified mkdocs builds without warnings or errors

Standard: Use kebab-case (lowercase-with-hyphens) for all markdown files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

docs/development/customer-auth-summary.md

@@ -1,7 +1,7 @@
 # Customer Authentication - Quick Summary
 
 **Date**: 2025-11-24
-**Full Documentation**: [CUSTOMER_AUTHENTICATION_IMPLEMENTATION.md](CUSTOMER_AUTHENTICATION_IMPLEMENTATION.md)
+**Full Documentation**: [customer-authentication-implementation.md](customer-authentication-implementation.md)
 
 ## What Was Implemented
 

docs/development/database-migrations.md

@@ -324,5 +324,5 @@ Migration failures will halt deployment to prevent data corruption.
 ## Further Reading
 
 - [Alembic Official Documentation](https://alembic.sqlalchemy.org/)
-- [Database Setup Guide](../getting-started/DATABASE_SETUP_GUIDE.md)
+- [Database Setup Guide](../getting-started/database-setup-guide.md)
 - [Deployment Guide](../deployment/production.md)

docs/development/database-seeder/database-quick-reference-guide.md

@@ -242,6 +242,6 @@ make help-db     # Database-specific help
 ```
 
 **Documentation**:
-- `DATABASE_INIT_GUIDE.md` - Detailed guide
+- `database-init-guide.md` - Detailed guide
 - `MIGRATION_GUIDE.md` - Migration from old system
 - `README.md` - Project overview