feat: 新增「部署客户端」日志采集器模块

三种采集器（host-promtail / k8s-daemonset / k8s-fluentbit-sidecar），每种关联已部署 Loki：
- host-promtail：SSH 安装 Promtail（复用 deployBinary）
- k8s-daemonset：helm 安装 Promtail DaemonSet（复用 deployHelm）
- k8s-fluentbit-sidecar：kubectl patch 注入 Fluent Bit sidecar

含 Collector 数据模型、三个部署器、配置模板、CRUD API、前端页面。
附带 UI 优化：ErrorBoundary、部署卡片浏览器访问按钮、菜单名称调整。

Co-Authored-By: Claude <noreply@anthropic.com>

backend/models/collector.go

@@ -0,0 +1,66 @@
+package models
+
+import "time"
+
+// Collector 日志采集器（部署客户端），关联一个已部署的 Loki 作为推送目标
+type Collector struct {
+	ID               uint            `json:"id"`
+	Name             string          `json:"name"`
+	Type             string          `json:"type"` // host-promtail | k8s-daemonset | k8s-fluentbit-sidecar
+	LokiDeploymentID uint            `json:"lokiDeploymentID"`
+	LokiDeployment   *LokiDeployment `json:"lokiDeployment,omitempty"`
+	RefType          string          `json:"refType"` // host | cluster
+	HostID           *uint           `json:"hostID,omitempty"`
+	Host             *Host           `json:"host,omitempty"`
+	ClusterID        *uint           `json:"clusterID,omitempty"`
+	Cluster          *Cluster        `json:"cluster,omitempty"`
+	TargetDeployment string          `json:"targetDeployment"` // sidecar 专用：目标 deployment 名
+	Namespace        string          `json:"namespace"`        // k8s 命名空间（默认 logging）
+	LogPath          string          `json:"logPath"`          // 采集日志路径
+	Labels           string          `json:"labels"`           // 额外标签（JSON）
+	Status           string          `json:"status"`           // pending | active | error
+	StatusMessage    string          `json:"statusMessage"`
+	Config           string          `json:"config"` // 生成的配置快照
+	CreatedAt        time.Time       `json:"createdAt"`
+	UpdatedAt        time.Time       `json:"updatedAt"`
+}
+
+func (c *Collector) Sanitized() map[string]interface{} {
+	var loki map[string]interface{}
+	if c.LokiDeployment != nil {
+		loki = map[string]interface{}{
+			"id":       c.LokiDeployment.ID,
+			"name":     c.LokiDeployment.Name,
+			"endpoint": c.LokiDeployment.Endpoint,
+			"status":   c.LokiDeployment.Status,
+		}
+	}
+	var host map[string]interface{}
+	if c.Host != nil {
+		host = c.Host.Sanitized()
+	}
+	var cluster map[string]interface{}
+	if c.Cluster != nil {
+		cluster = c.Cluster.Sanitized()
+	}
+	return map[string]interface{}{
+		"id":               c.ID,
+		"name":             c.Name,
+		"type":             c.Type,
+		"lokiDeploymentID": c.LokiDeploymentID,
+		"lokiDeployment":   loki,
+		"refType":          c.RefType,
+		"hostID":           c.HostID,
+		"host":             host,
+		"clusterID":        c.ClusterID,
+		"cluster":          cluster,
+		"targetDeployment": c.TargetDeployment,
+		"namespace":        c.Namespace,
+		"logPath":          c.LogPath,
+		"labels":           c.Labels,
+		"status":           c.Status,
+		"statusMessage":    c.StatusMessage,
+		"createdAt":        c.CreatedAt,
+		"updatedAt":        c.UpdatedAt,
+	}
+}