refactor: extract etcp_router_recv_cb into 5 functions + fix send_q threshold

- router_verify_signature — Ed25519 signature verification
- router_handle_ack — ACK processing + drain on send_blocked
- router_forward_transit — packet forwarding
- router_check_peer_restart — session restart + RST detection
- router_handle_data_packet — reorder/assembly/dedup
- free_entry helper
- etcp_router_recv_cb: 198 → 42 lines
- ROUTER_MAX_SEND_Q_PACKETS threshold: MAX/2 → MAX-1 (min wait)

src/proxy/tcp_proxy_server.c

@@ -212,7 +212,6 @@ static void read_queue_drain_cb(struct ll_queue* q, void* arg) {
     struct UTUN_INSTANCE* inst = rc->ctx ? rc->ctx->inst : NULL;
     struct ll_entry* e;
 
-    // Сначала добиваем отложенный tx_buf — force=1 чтобы обойти backpressure
     if (rc->tx_buf) {
         int ret = send_msg(inst, rc->peer_node_id, TCP_PROXY_SUBCMD_DATA, rc->stream_id, rc->tx_buf, rc->tx_len, 0);
         if (ret == 0) {
@@ -248,9 +247,8 @@ static void read_queue_drain_cb(struct ll_queue* q, void* arg) {
     }
     int ret = send_msg(inst, rc->peer_node_id, TCP_PROXY_SUBCMD_DATA, rc->stream_id, e->dgram, e->len, 0);
     rc->bytes_relayed += e->len; rc->drain_count++;
-    if ((rc->drain_count & 63) == 0 || rc->drain_count <= 4)
-        DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "TPS DRAIN #%u sid=%08x len=%u → ret=%d sent=%u recv=%u relayed=%u",
-                   rc->drain_count, rc->stream_id, e->len, ret, rc->bytes_sent, rc->bytes_recv, rc->bytes_relayed);
+    DEBUG_TRACE(DEBUG_CATEGORY_TRAFFIC, "TPS DRAIN #%u sid=%08x len=%u → ret=%d rq=%d",
+               rc->drain_count, rc->stream_id, e->len, ret, q->count);
     if (ret == 0) {
         memory_pool_free(rc->tc->data_pool, e->dgram); queue_entry_free(e);
         queue_resume_callback(q);
@@ -270,6 +268,9 @@ static void pause_resume_cb(struct ll_queue* q, void* arg) {
     (void)q;
     struct tcp_proxy_server_conn* rc = (struct tcp_proxy_server_conn*)arg;
     if (!rc->tc || rc->tc->sock == SOCKET_INVALID || rc->cli_closed) return;
+    DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "TPS RESUME sid=%08x tx_buf=%s rq=%d",
+               rc->stream_id, rc->tx_buf ? "y" : "n",
+               rc->tc->read_queue ? rc->tc->read_queue->count : 0);
     queue_resume_callback(rc->tc->read_queue);
 }
 
@@ -378,9 +379,8 @@ int tcp_proxy_server_handle_data(struct UTUN_INSTANCE* inst, struct ETCP_CONN* c
     }
     size_t data_len = entry->len - TCP_PROXY_HDR_SIZE;
     rc->bytes_sent += (uint32_t)data_len; rc->data_count++;
-    if ((rc->data_count & 63) == 0 || rc->data_count <= 4)
-        DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "TPS DATA #%u sid=%08x len=%zu sent=%u recv=%u relayed=%u",
-                   rc->data_count, stream_id, data_len, rc->bytes_sent, rc->bytes_recv, rc->bytes_relayed);
+    DEBUG_TRACE(DEBUG_CATEGORY_TRAFFIC, "TPS DATA #%u sid=%08x len=%zu",
+               rc->data_count, stream_id, data_len);
     if (data_len > 0) {
         if (data_len > rc->tc->data_pool->object_size) {
             DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_proxy_server: data_len=%zu > pool_sz=%zu, dropping sid=%08x",