feat: 多主机纳管、用户认证、noVNC控制台、深色主题

主要功能:
- 多主机管理: 支持TCP/SSH方式纳管远程KVM主机
- 用户认证: JWT token认证, 默认admin/admin123
- noVNC控制台: 前端集成noVNC, WebSocket代理VNC连接
- 深色主题: 全局Element Plus深色主题覆盖
- 虚拟机操作: 克隆、迁移、XML编辑、快照管理
- 资源监控: CPU/内存/磁盘IO/网络流量实时监控

Bug修复:
- libvirt getInfo()内存单位修正(MiB非KiB)
- 远程主机VNC 0.0.0.0监听地址连接策略修复
- Dashboard定时器内存泄漏修复
- bcrypt版本兼容性修复

backend/app/routers/monitor.py

@@ -1,6 +1,6 @@
 """资源监控路由"""
-from fastapi import APIRouter, HTTPException
-from app.libvirt_conn import libvirt_conn
+from fastapi import APIRouter, HTTPException, Query
+from app.libvirt_conn import conn_pool
 import libvirt
 import time
 import threading
@@ -13,23 +13,19 @@ _cache_lock = threading.Lock()
 
 
 @router.get("/overview")
-async def monitor_overview():
+async def monitor_overview(host_id: str = Query("local")):
     """宿主机总览监控"""
-    conn = libvirt_conn.conn
+    conn = conn_pool.get_conn(host_id)
 
-    # 宿主机信息
     host_info = conn.getInfo()
     hostname = conn.getHostname()
 
-    # CPU 使用率（通过 node info）
-    cpu_stats = conn.getCPUStats(-1, 0)  # 全局 CPU 统计
+    cpu_stats = conn.getCPUStats(-1, 0)
     cpu_total = cpu_stats.get("user", 0) + cpu_stats.get("system", 0) + cpu_stats.get("idle", 0)
     cpu_used = cpu_stats.get("user", 0) + cpu_stats.get("system", 0)
     cpu_percent = round(cpu_used / cpu_total * 100, 1) if cpu_total > 0 else 0
 
-    # 内存
     memory_total_kb = host_info[1]
-    # 获取可用内存
     try:
         with open("/proc/meminfo", "r") as f:
             meminfo = {}
@@ -48,7 +44,6 @@ async def monitor_overview():
         mem_available_mb = mem_total_mb
         mem_percent = 0
 
-    # 虚拟机统计
     domains = conn.listAllDomains(0)
     running = sum(1 for d in domains if d.isActive())
     stopped = len(domains) - running
@@ -75,9 +70,9 @@ async def monitor_overview():
 
 
 @router.get("/vm/{name}")
-async def monitor_vm(name: str):
+async def monitor_vm(name: str, host_id: str = Query("local")):
     """获取虚拟机实时监控数据"""
-    conn = libvirt_conn.conn
+    conn = conn_pool.get_conn(host_id)
     try:
         dom = conn.lookupByName(name)
     except libvirt.libvirtError:
@@ -86,10 +81,9 @@ async def monitor_vm(name: str):
     if not dom.isActive():
         return {"name": name, "state": "stopped", "cpu_percent": 0, "memory": {}}
 
-    # CPU 百分比
-    cpu_percent = _get_vm_cpu_percent(dom)
+    cache_key = f"{host_id}_{name}"
+    cpu_percent = _get_vm_cpu_percent(dom, cache_key)
 
-    # 内存
     mem_stats = {}
     try:
         raw = dom.memoryStats()
@@ -104,10 +98,7 @@ async def monitor_vm(name: str):
     except Exception:
         pass
 
-    # 磁盘IO
     disk_stats = _get_vm_disk_stats(dom)
-
-    # 网络IO
     net_stats = _get_vm_net_stats(dom)
 
     return {
@@ -120,17 +111,13 @@ async def monitor_vm(name: str):
     }
 
 
-def _get_vm_cpu_percent(dom) -> float:
+def _get_vm_cpu_percent(dom, cache_key: str) -> float:
     """计算虚拟机 CPU 使用率"""
-    cache_key = f"cpu_{dom.name()}"
-
     try:
-        # 第一次采样
         info1 = dom.info()
         cpu_time1 = info1[2]
         t1 = time.time()
 
-        # 从缓存获取上一次数据
         with _cache_lock:
             prev = _stats_cache.get(cache_key)
 
@@ -138,13 +125,11 @@ def _get_vm_cpu_percent(dom) -> float:
             cpu_time0, t0 = prev
             elapsed = t1 - t0
             cpu_diff = cpu_time1 - cpu_time0
-            # CPU时间单位是纳秒
             cpu_percent = round((cpu_diff / 1e9) / elapsed * 100, 1)
             cpu_percent = min(cpu_percent, 100.0)
         else:
             cpu_percent = 0.0
 
-        # 更新缓存
         with _cache_lock:
             _stats_cache[cache_key] = (cpu_time1, t1)