Add test infrastructure with fixtures, helpers, and integration tests

- Add [lib] target to enable integration test imports
- Add rcgen and reqwest dev-dependencies for TLS and HTTP test helpers
- Create src/config/test_fixtures.rs with test_static_config() and test_dynamic_config()
- Create tests/ with integration tests, HTTP test helper (TestUpstream), and TLS test helper (SelfSignedCert)
- Add Clone derives to StaticConfig and related structs for test fixture construction
- All existing tests continue to pass

src/config/test_fixtures.rs

@@ -0,0 +1,65 @@
+use crate::config::dynamic_config::{BodyConfig, DynamicConfig, RateLimitConfig, SiteConfig};
+use crate::config::static_config::{ListenerConfig, LoggingConfig, StaticConfig, TlsConfig};
+
+pub fn test_static_config() -> StaticConfig {
+    StaticConfig {
+        listeners: vec![ListenerConfig {
+            bind_addr: "127.0.0.1".to_string(),
+            http_port: 80,
+            https_port: 443,
+            tls: TlsConfig {
+                mode: "manual".to_string(),
+                acme_domains: vec![],
+                acme_cache_dir: String::new(),
+                acme_directory: "production".to_string(),
+                cert_path: "/tmp/test-cert.pem".to_string(),
+                key_path: "/tmp/test-key.pem".to_string(),
+            },
+            sites: vec![],
+        }],
+        allow_wildcard_bind: false,
+        health_check_port: 9900,
+        admin_socket_path: "/tmp/reverse-proxy-test/admin.sock".to_string(),
+        shutdown_timeout_secs: 30,
+        logging: LoggingConfig::default(),
+    }
+}
+
+pub fn test_dynamic_config() -> DynamicConfig {
+    DynamicConfig {
+        sites: vec![SiteConfig {
+            host: "test.local".to_string(),
+            upstream: "127.0.0.1:8080".to_string(),
+            upstream_scheme: "http".to_string(),
+            upstream_connect_timeout_secs: 5,
+            upstream_request_timeout_secs: 60,
+        }],
+        rate_limit: RateLimitConfig {
+            requests_per_second: 10,
+            burst: 20,
+        },
+        body: BodyConfig {
+            limit_bytes: 104857600,
+        },
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_static_config_fixture_is_valid() {
+        let config = test_static_config();
+        assert!(!config.listeners.is_empty());
+        assert_eq!(config.health_check_port, 9900);
+    }
+
+    #[test]
+    fn test_dynamic_config_fixture_is_valid() {
+        let config = test_dynamic_config();
+        assert!(!config.sites.is_empty());
+        assert_eq!(config.rate_limit.requests_per_second, 10);
+        assert_eq!(config.body.limit_bytes, 104857600);
+    }
+}