Phase 1: Foundation - CI/CD, systemd service, test framework

Completed Phase 1 foundation tasks:
- CI/CD pipeline (.github/workflows/ci.yml)
  - Format check (rustfmt)
  - Clippy lints
  - Unit tests with codecov
  - Security audit (cargo-audit)
  - Build release artifacts
  - Ubuntu package build
- Systemd service file (configs/linux-patch-api.service)
  - Security hardening (ProtectSystem, SystemCallFilter)
  - Journal logging integration
  - Resource limits
- Test framework structure (tests/unit/, tests/integration/)
  - Initial unit test template
  - Test framework verified with cargo test

Rust toolchain 1.94.1 installed and verified.

tests/unit/config.rs

@@ -0,0 +1,28 @@
+//! Unit Tests - Configuration Module
+//!
+//! Tests for configuration loading and validation.
+
+use linux_patch_api::AppConfig;
+
+#[test]
+fn test_config_load_valid_yaml() {
+    // TODO: Create test fixtures
+    // let result = AppConfig::load("fixtures/valid_config.yaml");
+    // assert!(result.is_ok());
+}
+
+#[test]
+fn test_config_load_missing_file() {
+    let result = AppConfig::load("/nonexistent/path/config.yaml");
+    assert!(result.is_err());
+}
+
+#[test]
+fn test_config_validation_port() {
+    // TODO: Test port validation (1-65535)
+}
+
+#[test]
+fn test_config_validation_bind_address() {
+    // TODO: Test bind address validation
+}