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/host.py

@@ -0,0 +1,116 @@
+"""主机管理路由"""
+from fastapi import APIRouter, HTTPException
+from app.hosts import (
+    list_hosts, get_host, add_host, remove_host,
+    test_connection, update_host_status, HostCreate,
+)
+from app.libvirt_conn import conn_pool
+import time
+
+router = APIRouter()
+
+
+@router.get("/list")
+async def api_list_hosts():
+    """列出所有已注册主机"""
+    hosts = list_hosts()
+    result = []
+    for h in hosts:
+        info = h.model_dump()
+        # 尝试获取实时状态
+        try:
+            mgr = conn_pool.get(h.id)
+            conn = mgr.conn
+            alive = conn.isAlive()
+            info["status"] = "online" if alive else "offline"
+            if alive:
+                host_data = conn.getInfo()
+                info["cpu_cores"] = host_data[2]
+                info["memory_mb"] = host_data[1]  # getInfo()[1] 已经是 MiB 单位
+                info["hostname"] = conn.getHostname()
+                # 虚拟机数
+                domains = conn.listAllDomains(0)
+                info["vm_total"] = len(domains)
+                info["vm_running"] = sum(1 for d in domains if d.isActive())
+            update_host_status(h.id, info["status"])
+        except Exception:
+            info["status"] = "offline"
+            update_host_status(h.id, "offline")
+        result.append(info)
+    return {"hosts": result, "total": len(result)}
+
+
+@router.get("/detail/{host_id}")
+async def api_get_host(host_id: str):
+    """获取单台主机详情"""
+    host = get_host(host_id)
+    if not host:
+        raise HTTPException(status_code=404, detail=f"主机 '{host_id}' 不存在")
+    info = host.model_dump()
+    try:
+        mgr = conn_pool.get(host_id)
+        info["host_info"] = mgr.get_host_info()
+        info["status"] = "online"
+        # 虚拟机数
+        domains = mgr.conn.listAllDomains(0)
+        info["vm_total"] = len(domains)
+        info["vm_running"] = sum(1 for d in domains if d.isActive())
+        update_host_status(host_id, "online")
+    except Exception as e:
+        info["status"] = "offline"
+        info["error"] = str(e)
+        update_host_status(host_id, "offline")
+    return info
+
+
+@router.post("/add")
+async def api_add_host(req: HostCreate):
+    """添加新主机"""
+    # 先测试连接
+    result = test_connection(req.uri)
+    if not result["success"]:
+        raise HTTPException(status_code=400, detail=f"连接测试失败: {result['error']}")
+
+    host = add_host(req)
+    # 更新状态为在线
+    update_host_status(host.id, "online")
+    return {"message": f"主机 '{host.name}' 添加成功", "host": host.model_dump()}
+
+
+@router.delete("/delete/{host_id}")
+async def api_delete_host(host_id: str):
+    """删除主机"""
+    if host_id == "local":
+        raise HTTPException(status_code=400, detail="不能删除本机")
+    if not remove_host(host_id):
+        raise HTTPException(status_code=404, detail=f"主机 '{host_id}' 不存在")
+    conn_pool.remove(host_id)
+    return {"message": f"主机 '{host_id}' 已删除"}
+
+
+@router.post("/test")
+async def api_test_connection(req: HostCreate):
+    """测试连接（不添加主机）"""
+    result = test_connection(req.uri)
+    return result
+
+
+@router.post("/refresh/{host_id}")
+async def api_refresh_host(host_id: str):
+    """刷新主机状态"""
+    host = get_host(host_id)
+    if not host:
+        raise HTTPException(status_code=404, detail=f"主机 '{host_id}' 不存在")
+    try:
+        # 重新建立连接
+        conn_pool.remove(host_id)
+        mgr = conn_pool.get(host_id)
+        conn = mgr.conn
+        alive = conn.isAlive()
+        status = "online" if alive else "offline"
+        update_host_status(host_id, status)
+        return {"status": status, "hostname": conn.getHostname()}
+    except Exception as e:
+        update_host_status(host_id, "offline")
+        conn_pool.remove(host_id)
+        return {"status": "offline", "error": str(e)}