Add comprehensive security tests for quota management and relay functionality

- Introduced `relay_dual_lock_race_harness_security_tests.rs` to validate user liveness during lock hold and release cycles.
- Added `relay_quota_extended_attack_surface_security_tests.rs` to cover various quota scenarios including positive, negative, edge cases, and adversarial conditions.
- Implemented `relay_quota_lock_eviction_lifecycle_tdd_tests.rs` to ensure proper eviction of stale entries and lifecycle management of quota locks.
- Created `relay_quota_lock_eviction_stress_security_tests.rs` to stress test the eviction mechanism under high churn conditions.
- Enhanced `relay_quota_lock_pressure_adversarial_tests.rs` to verify reclaiming of unreferenced entries after explicit eviction.
- Developed `relay_quota_retry_allocation_latency_security_tests.rs` to benchmark and validate latency and allocation behavior under contention.

src/proxy/tests/masking_interface_cache_concurrency_security_tests.rs

@@ -0,0 +1,41 @@
+#![cfg(unix)]
+
+use super::*;
+use std::sync::{Mutex, OnceLock};
+use tokio::sync::Barrier;
+
+fn interface_cache_test_lock() -> &'static Mutex<()> {
+    static LOCK: OnceLock<Mutex<()>> = OnceLock::new();
+    LOCK.get_or_init(|| Mutex::new(()))
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn adversarial_parallel_cold_miss_performs_single_interface_refresh() {
+    let _guard = interface_cache_test_lock()
+        .lock()
+        .unwrap_or_else(|poison| poison.into_inner());
+    reset_local_interface_enumerations_for_tests();
+
+    let local_addr: SocketAddr = "0.0.0.0:443".parse().expect("valid local addr");
+    let workers = 32usize;
+    let barrier = std::sync::Arc::new(Barrier::new(workers));
+    let mut tasks = Vec::with_capacity(workers);
+
+    for _ in 0..workers {
+        let barrier = std::sync::Arc::clone(&barrier);
+        tasks.push(tokio::spawn(async move {
+            barrier.wait().await;
+            is_mask_target_local_listener_async("127.0.0.1", 443, local_addr, None).await
+        }));
+    }
+
+    for task in tasks {
+        let _ = task.await.expect("parallel cache task must not panic");
+    }
+
+    assert_eq!(
+        local_interface_enumerations_for_tests(),
+        1,
+        "parallel cold misses must coalesce into a single interface enumeration"
+    );
+}