深度优化: 修复跨服务器登录、密码哈希、仪表盘UI、流量趋势等12项问题

### 严重修复
1. 跨服务器无法登录 - 新增SESSION_COOKIE_DOMAIN/SECURE/NAME配置
2. SOCKS5用户密码明文存储→bcrypt哈希（兼容自动迁移）
3. 仪表盘审计日志不显示→替换为空循环为真实API加载
4. 管理员登录防爆破未生效→auth.py集成check_fail2ban

### 中等问题修复
5. 流量趋势图表无数据→新增record_traffic_snapshot后台线程
6. 网络流量累计值跳变→新增基线差值机制
7. asyncio连接计数非线程安全→加锁保护

### 优化改进
8. API密钥页面截断文本修复
9. 新增gunicorn/bcrypt依赖
10. 更新README环境变量文档和生产建议
11. 登录密码常量时间对比防时序攻击
12. 仪表盘图表添加animation:false防卡顿

services/stats_service.py

@@ -1,4 +1,5 @@
 """监控与统计服务。"""
+import copy
 import logging
 import os
 import psutil
@@ -14,13 +15,34 @@ log = logging.getLogger("socks.stats")
 _metrics_buffer = deque(maxlen=600)  # 10分钟 @ 10秒间隔
 _metrics_lock = __import__("threading").Lock()
 
+# 网络流量基线（用于计算会话增量）
+_net_baseline = None
+_net_baseline_lock = __import__("threading").Lock()
+
+
+def _get_net_delta():
+    global _net_baseline
+    try:
+        net = psutil.net_io_counters()
+        current = {"bytes_sent": net.bytes_sent, "bytes_recv": net.bytes_recv}
+        with _net_baseline_lock:
+            if _net_baseline is None:
+                _net_baseline = copy.deepcopy(current)
+                return {"bytes_sent": 0, "bytes_recv": 0}
+            return {
+                "bytes_sent": current["bytes_sent"] - _net_baseline["bytes_sent"],
+                "bytes_recv": current["bytes_recv"] - _net_baseline["bytes_recv"],
+            }
+    except Exception:
+        return {"bytes_sent": 0, "bytes_recv": 0}
+
 
 def _record_metrics():
     """记录系统级指标。"""
     try:
         cpu = psutil.cpu_percent(interval=0.5)
         mem = psutil.virtual_memory()
-        net = psutil.net_io_counters()
+        net_delta = _get_net_delta()
         # 计算活跃连接
         with db.app.app_context():
             active = db.session.query(Connection).filter_by(
@@ -32,8 +54,8 @@ def _record_metrics():
             "mem_percent": mem.percent,
             "mem_used_mb": mem.used // 1024 // 1024,
             "mem_total_mb": mem.total // 1024 // 1024,
-            "net_bytes_sent": net.bytes_sent,
-            "net_bytes_recv": net.bytes_recv,
+            "net_bytes_sent": net_delta["bytes_sent"],
+            "net_bytes_recv": net_delta["bytes_recv"],
             "active_connections": active,
         }
         with _metrics_lock:
@@ -195,3 +217,34 @@ def prune_old_data():
         )
         db.session.commit()
         log.info("数据清理完成")
+
+
+def record_traffic_snapshot():
+    """记录每日流量快照（用于流量趋势图表）。"""
+    from datetime import date
+    today = date.today()
+    with db.app.app_context():
+        from sqlalchemy import func
+        today_start = datetime.now(timezone.utc).replace(hour=0, minute=0, second=0, microsecond=0)
+        result = db.session.query(
+            func.coalesce(func.sum(Connection.bytes_in), 0),
+            func.coalesce(func.sum(Connection.bytes_out), 0),
+            func.count(Connection.id),
+        ).filter(Connection.started_at >= today_start).first()
+        total_in = result[0] if result else 0
+        total_out = result[1] if result else 0
+        total_conns = result[2] if result else 0
+
+        snap = db.session.query(TrafficSnapshot).filter_by(date=today).first()
+        if snap:
+            snap.bytes_in = total_in
+            snap.bytes_out = total_out
+            snap.connections = total_conns
+        else:
+            snap = TrafficSnapshot(
+                date=today, bytes_in=total_in, bytes_out=total_out,
+                connections=total_conns,
+            )
+            db.session.add(snap)
+        db.session.commit()
+        log.info("流量快照已记录: %s", today)