Initial commit: Vault Hierarchical Initializer

This commit adds the full implementation of vault-hier, a Rust utility for:
- Initializing HashiCorp Vault in production mode (non-dev)
- Handling Vault seal/unseal operations with key thresholds
- Using Docker Compose for containerized operation
- Supporting persistent storage via Docker volumes

Key components:
- Rust application for Vault interaction
- Docker and Docker Compose configuration
- Test scripts for local development
- Nix flake for development dependencies

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

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

.gitignore

@@ -0,0 +1,34 @@
+# Rust build artifacts
+/target/
+**/*.rs.bk
+*.pdb
+Cargo.lock
+
+# Generated by Cargo
+.cargo/
+
+# Direnv
+.direnv/
+.envrc
+
+# Vault related files
+vault-credentials.txt
+vault-config/
+
+# Temporary test files
+docker-compose-test.yml
+test_vault.sh
+
+# IDE files
+.idea/
+.vscode/
+*.iml
+*.swp
+*~
+
+# Nix
+result
+result-*
+
+# macOS specific files
+.DS_Store