docs: rename DEVELOPMENT.md to development.md and update links

- Rename docs/contributing/DEVELOPMENT.md to development.md (lowercase)
- Update all references from DEVELOPMENT.md to Development.md (titlecase links)
- Update docs/contributing/contributing.md
- Update docs/index.md

docs/contributing/contributing.md

@@ -4,7 +4,7 @@ Welcome to the Bookhoard contributing documentation. This section contains guide
 
 ## 🚀 Getting Started
 
-- **[Development Guide](DEVELOPMENT.md)** - Development workflow and architecture
+- **[Development Guide](Development.md)** - Development workflow and architecture
   - Architecture overview
   - Directory structure
   - Local development setup
@@ -22,7 +22,7 @@ Welcome to the Bookhoard contributing documentation. This section contains guide
 
 ## 🤝 How to Contribute
 
-We welcome contributions! Please see our [Development Guide](DEVELOPMENT.md) for information on:
+We welcome contributions! Please see our [Development Guide](Development.md) for information on:
 - Setting up your development environment
 - Understanding the codebase
 - Making pull requests