feat: Complete rewrite of secrets management with production-ready bash script

Major enhancements:
- New secrets-manager.sh script with comprehensive functionality
- Automated Bitwarden CLI installation (snap/npm/direct download)
- Configuration file management with sample template
- Multiple commands: install, get, list, test
- Robust error handling with specific exit codes
- Comprehensive logging and session cleanup
- Security improvements: proper gitignore, credential protection

Documentation:
- Complete README rewrite with detailed usage examples
- Installation instructions and troubleshooting guide
- Command reference and error code documentation
- Security considerations and best practices

Files added:
- secrets-manager.sh: Main production script (replaces poc.sh approach)
- bitwarden-config.conf.sample: Configuration template
- .gitignore: Protects credentials and temporary files

This version combines lessons learned from poc.sh and prod.sh attempts,
providing a single, reliable solution for Bitwarden CLI management on Linux.

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

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

.gitignore

@@ -0,0 +1,25 @@
+# Bitwarden configuration files containing secrets
+bitwarden-config.conf
+*.conf
+
+# Log files
+*.log
+/tmp/*.log
+
+# Session files
+.bw-session
+
+# Backup files
+*.bak
+*.backup
+
+# OS specific files
+.DS_Store
+Thumbs.db
+
+# Editor files
+*.swp
+*.swo
+*~
+.vscode/
+.idea/