docs: rename INDEX files to meaningful names and fix navigation

- 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.

docs/operations/operations.md

@@ -0,0 +1,34 @@
+# Operations Documentation
+
+Welcome to the Bookhoard operations documentation. This section contains guides for deploying, maintaining, and troubleshooting Bookhoard instances.
+
+## 🔧 Deployment
+
+### Quick Start
+
+1. **[Troubleshooting Guide](troubleshooting.md)** - Common deployment issues and solutions
+   - Environment variables setup
+   - Port conflicts
+   - Container runtime (Podman)
+   - Network configuration
+   - Performance optimization
+
+### Additional Deployment Guides
+
+**[Deployment Guide](deployment.md)** - Comprehensive deployment guide
+- *Coming Soon*
+
+## 🛠️ Maintenance
+
+**[Maintenance Guide](maintenance.md)** - Ongoing operations and maintenance
+- *Coming Soon*
+
+## 📊 Monitoring
+
+**[Monitoring Guide](monitoring.md)** - Monitoring and alerting
+- *Coming Soon*
+
+---
+
+**Looking for user documentation?** See the [User Portal](../user/INDEX.md)
+**Need API docs?** See the [Developer Portal](../developer/INDEX.md)