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>

bitwarden-config.conf.sample

@@ -0,0 +1,16 @@
+# Bitwarden Configuration File
+# Copy this file to bitwarden-config.conf and update with your actual values
+
+# Bitwarden server URL
+BW_SERVER_URL="https://pwvault.turnsys.com"
+
+# API credentials (get these from your Bitwarden account settings)
+BW_CLIENTID="your_client_id_here"
+BW_CLIENTSECRET="your_client_secret_here"
+
+# Master password for your Bitwarden account
+BW_PASSWORD="your_master_password_here"
+
+# Optional: Additional environment variables
+# BW_ORGANIZATION_ID="your_org_id_here"
+# BW_COLLECTION_ID="your_collection_id_here"