stcp: ed25519 pubkey exchange in handshake, fix instance destroy segfault, fix chat_tcp_test

- u_async.c: process immediate_queue BEFORE epoll_wait in uasync_poll
- stcp_link.c: defensive NULL etcp_conn/etcp_link in stcp_link_close
- utun_instance.c: move stcp_server_list_destroy_all to Phase J (before ETCP),
  add deferred drain in both Phase J and L
- stcp.h/c: STCP_HS_ENC_CLIENT 6→38, STCP_HS_ENC_SERVER 7→39,
  exchange ed25519_pubkey in both handshake directions
- etcp_connections.c: copy peer_ed25519 from STCP to ETCP_CONN in
  etcp_link_enter_ready_tcp; guard link->etcp in tcp_link_close_cb
- chat_sync.c: fix lk->conn NULL dereference for TCP links
- test_stcp.c: update stcp_server_create/stcp_client_connect callsites
- tools/chat_tcp_test: change transport udp→tcp

tools/chatgui/src/storagesettingspage.cpp

@@ -0,0 +1,112 @@
+#include "storagesettingspage.h"
+#include "../db/db_manager.h"
+#include "../transport/gui_bridge.h"
+#include "../transport/config_updater.h"
+#include "../../lib/mem.h"
+extern "C" {
+#include "chat/chat_core.h"
+}
+#include <QVBoxLayout>
+#include <QFormLayout>
+#include <QCheckBox>
+#include <QSpinBox>
+#include <QLabel>
+#include <QFrame>
+
+static void saveUiStateInt(const char* key, int val) {
+    QByteArray v = QByteArray::number(val);
+    size_t klen = strlen(key), vlen = (size_t)v.size(), total = klen + 1 + vlen + 1;
+    if (total > 256) return;
+    void* arg = u_malloc(total);
+    memcpy(arg, key, klen + 1);
+    memcpy((char*)arg + klen + 1, v.constData(), vlen + 1);
+    gui_bridge_post_uasync_fn(chat_core_save_ui_state_trampoline, arg);
+}
+
+void postChatSetting(const QString& configPath, const char* name, int val) {
+    config_update_option(configPath, "chatserver", name, QString::number(val), CONFIG_UPDATE_REPLACE);
+    QByteArray v = QByteArray::number(val);
+    size_t nlen = strlen(name), vlen = (size_t)v.size(), total = nlen + 1 + vlen + 1;
+    if (total > 256) return;
+    void* arg = u_malloc(total);
+    memcpy(arg, name, nlen + 1);
+    memcpy((char*)arg + nlen + 1, v.constData(), vlen + 1);
+    gui_bridge_post_uasync_fn(chat_core_set_setting_trampoline, arg);
+}
+
+StorageSettingsPage::StorageSettingsPage(DbManager* db, QWidget* parent)
+    : QWidget(parent)
+    , m_db(db)
+{
+    auto* layout = new QVBoxLayout(this);
+    layout->setContentsMargins(0, 12, 0, 0);
+    layout->setSpacing(14);
+
+    auto* title = new QLabel("Media Storage", this);
+    title->setStyleSheet("font-weight: bold; font-size: 13px;");
+    layout->addWidget(title);
+
+    auto* form = new QFormLayout();
+    form->setSpacing(10);
+    form->setContentsMargins(0, 8, 0, 0);
+
+    m_autoloadCheck = new QCheckBox("Autoload media", this);
+    m_autoloadCheck->setStyleSheet("font-size: 13px;");
+    form->addRow(m_autoloadCheck);
+
+    m_autoloadMaxSize = new QSpinBox(this);
+    m_autoloadMaxSize->setRange(1, 500);
+    m_autoloadMaxSize->setSuffix(" MB");
+    m_autoloadMaxSize->setFixedWidth(110);
+    m_autoloadMaxSize->setStyleSheet(
+        "QSpinBox { border: 1px solid palette(mid); border-radius: 4px;"
+        " padding: 5px 8px; font-size: 13px; background: palette(base); }");
+    form->addRow("Autoload max size:", m_autoloadMaxSize);
+
+    m_maxStorageSize = new QSpinBox(this);
+    m_maxStorageSize->setRange(1, 100);
+    m_maxStorageSize->setSuffix(" GB");
+    m_maxStorageSize->setFixedWidth(110);
+    m_maxStorageSize->setStyleSheet(
+        "QSpinBox { border: 1px solid palette(mid); border-radius: 4px;"
+        " padding: 5px 8px; font-size: 13px; background: palette(base); }");
+    form->addRow("Max storage size:", m_maxStorageSize);
+
+    layout->addLayout(form);
+
+    auto* sep = new QFrame(this);
+    sep->setFrameShape(QFrame::HLine);
+    sep->setStyleSheet("QFrame { color: palette(mid); }");
+    layout->addWidget(sep);
+
+    layout->addStretch();
+}
+
+void StorageSettingsPage::loadFromDb() {
+    if (!m_db) return;
+
+    bool autoload = m_db->getUiStateInt("storage_autoload", 1);
+    m_autoloadCheck->setChecked(autoload);
+
+    int maxSizeMb = m_db->getUiStateInt("storage_autoload_maxsize_mb", 10);
+    m_autoloadMaxSize->setValue(maxSizeMb);
+
+    int maxGb = m_db->getUiStateInt("storage_maxsize_gb", 1);
+    m_maxStorageSize->setValue(maxGb);
+}
+
+void StorageSettingsPage::applyAndSave() {
+    int autoload        = m_autoloadCheck->isChecked() ? 1 : 0;
+    int autoloadMaxSize = m_autoloadMaxSize->value();
+    int maxGb           = m_maxStorageSize->value();
+
+    saveUiStateInt("storage_autoload", autoload);
+    saveUiStateInt("storage_autoload_maxsize_mb", autoloadMaxSize);
+    saveUiStateInt("storage_maxsize_gb", maxGb);
+
+    if (!m_configPath.isEmpty()) {
+        postChatSetting(m_configPath, "storage_autoload", autoload);
+        postChatSetting(m_configPath, "storage_autoload_maxsize_mb", autoloadMaxSize);
+        postChatSetting(m_configPath, "storage_maxsize_gb", maxGb);
+    }
+}