fix: proxy ERROR loop, BBR test backpressure, O(1) u_free, test ordering

- tcp_proxy: ERROR silently dropped (no ERROR->ERROR loop), Russian removed from logs
- etcp_bbr: swap min(lo) and max(4*mss) in bbr_bound_cwnd_for_inflight_model
- test_etcp_bbr: fix cwnd comparison (packets vs bytes)
- ll_queue: double-put detection (abort), Floyd cycle detection in consistency check
- ll_queue: QUEUE_DEBUG commented out (was always-on, O(N) per put)
- mem: u_free_impl now O(1) via doubly-linked list, double-free detection
- bbr_integration: queue_waiter_wait + call_soon backpressure (threshold=1)
- tests/Makefile.am: fast tests first, *.log cleanup before run

lib/ll_queue.c

@@ -309,6 +309,12 @@ int queue_data_put(struct ll_queue* q, struct ll_entry* entry) {
     queue_check_thread(q);
 #endif
 
+    if (entry->prev || entry->next || q->head == entry || q->tail == entry) {
+        DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "[%s] double put detected! entry=%p prev=%p next=%p len=%u",
+                    q->name, (void*)entry, (void*)entry->prev, (void*)entry->next, entry->len);
+        abort();
+    }
+
     if (q->hash_size > 0) {
         DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "[%s] Put no-hash data to hash queue",q->name);
         queue_dgram_free(entry);
@@ -350,6 +356,12 @@ int queue_data_put_with_index(struct ll_queue* q, struct ll_entry* entry) {
     queue_check_thread(q);
 #endif
 
+    if (entry->prev || entry->next || q->head == entry || q->tail == entry) {
+        DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "[%s] double put_with_index detected! entry=%p prev=%p next=%p",
+                    q->name, (void*)entry, (void*)entry->prev, (void*)entry->next);
+        abort();
+    }
+
     if (q->index_size == 0 || (size_t)q->index_offset + q->index_size > (size_t)entry->size) {
         DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "[%s] invalid index: offset=%u size=%u (data_size=%u)",q->name, q->index_offset, q->index_size, entry->size);
         queue_dgram_free(entry);
@@ -393,6 +405,12 @@ int queue_data_put_first(struct ll_queue* q, struct ll_entry* entry) {
     queue_check_thread(q);
 #endif
 
+    if (entry->prev || entry->next || q->head == entry || q->tail == entry) {
+        DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "[%s] double put_first detected! entry=%p prev=%p next=%p",
+                    q->name, (void*)entry, (void*)entry->prev, (void*)entry->next);
+        abort();
+    }
+
     if (q->hash_size > 0) {
         DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "[%s] Put no-hash data to hash queue",q->name);
         queue_dgram_free(entry);
@@ -426,6 +444,12 @@ int queue_data_put_first_with_index(struct ll_queue* q, struct ll_entry* entry)
     queue_check_thread(q);
 #endif
 
+    if (entry->prev || entry->next || q->head == entry || q->tail == entry) {
+        DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "[%s] double put_first_with_index detected! entry=%p prev=%p next=%p",
+                    q->name, (void*)entry, (void*)entry->prev, (void*)entry->next);
+        abort();
+    }
+
     if (q->index_size == 0 || (size_t)q->index_offset + q->index_size > (size_t)entry->size) {
         DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "[%s] invalid index: offset=%u size=%u (data_size=%u)",q->name, q->index_offset, q->index_size, entry->size);
         queue_dgram_free(entry);
@@ -505,14 +529,27 @@ int queue_entry_count(struct ll_queue* q) {
 // Функция проверки консистентности count и total_bytes
 // Возвращает 0 если ok, -1 если есть несоответствия
 int queue_check_consistency(struct ll_queue* q) {
-    if (!q) return -1; // Недопустимая очередь
+    if (!q) return -1;
     
-    // Проверка: если count > 0, то head не должен быть NULL
     if (q->count > 0 && !q->head) {
         DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "Queue '%s': count=%d but head is NULL!",
                     q->name ? q->name : "unknown", q->count);
         return -1;
     }
+
+    // Floyd cycle detection — за O(N) без риска зависания
+    {
+        struct ll_entry *slow = q->head, *fast = q->head;
+        while (fast && fast->next) {
+            slow = slow->next;
+            fast = fast->next->next;
+            if (slow == fast) {
+                DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "Queue '%s': CYCLE detected! entry=%p count=%d",
+                            q->name ? q->name : "unknown", (void*)slow, q->count);
+                abort();
+            }
+        }
+    }
     
     int actual_count = 0;
     size_t actual_bytes = 0;
@@ -523,7 +560,6 @@ int queue_check_consistency(struct ll_queue* q) {
         actual_bytes += current->int_len;
         if (current->next) {
             if (current->next->prev != current) {
-                // Несоответствие в связях prev/next
                 DEBUG_ERROR(DEBUG_CATEGORY_LL_QUEUE, "Queue '%s': prev/next error at entry %p != %p entries: %d!=%d bytes: %zu!=%zu",
                           q->name ? q->name : "unknown", (void*)current, (void*)current->next->prev, actual_count, q->count, actual_bytes, q->total_bytes);
                 return -1;