feat(i18n): CredFormDialog + ClusterComparePage 全量国际化 — 75 新增翻译键

- CredFormDialog.tsx: 凭据表单弹框全量迁移 (deploy.cred.form.* 37 键)
  SSH/Docker/TLS/AKSK/Database/API/Generic 7 种类型表单字段全覆盖
- ClusterComparePage.tsx: 多集群对比看板全量迁移 (k8s.compare.* 35 键)
  图表标签/表头/状态/空状态/标题全部国际化
- 新增 common.username/password/port 3 个通用键
- 翻译键总数 6182 → 6257 (zh-CN/en-US 完全对齐)
- tsc -b=0, npm build=✅ (20.76s), ESLint=0, 17/17 集成测试通过

frontend/src/locales/en-US.json

@@ -519,7 +519,10 @@
     "yesterday": "Yesterday",
     "zone": "Zone",
     "zoomIn": "Zoom In",
-    "zoomOut": "Zoom Out"
+    "zoomOut": "Zoom Out",
+    "username": "Username",
+    "password": "Password",
+    "port": "Port"
   },
   "menu": {
     "dashboard": "Dashboard",
@@ -1412,7 +1415,46 @@
       "selectDockerPwd": "Select Docker password credential",
       "selectApiCred": "Select credential (API/password etc.)",
       "selectCred": "Select credential",
-      "linkedCred": "Linked Credential"
+      "linkedCred": "Linked Credential",
+      "form": {
+        "editTitle": "Edit Credential",
+        "newTitle": "Add Credential",
+        "basicInfo": "Basic Information",
+        "credNamePlaceholder": "e.g. Production SSH",
+        "varAlias": "Variable Alias",
+        "varAliasPlaceholder": "e.g. MYSQL_PROD",
+        "tagsPlaceholder": "production, aliyun",
+        "descPlaceholder": "Optional remarks",
+        "typeConfig": "Configuration",
+        "editHint": "(only fill fields you want to change)",
+        "sshUser": "SSH User",
+        "sshPort": "SSH Port",
+        "sshPassword": "SSH Password",
+        "sshPwdPlaceholder": "Password (or leave empty to use key)",
+        "privateKey": "Private Key",
+        "privateKeyPlaceholder": "Paste SSH private key...",
+        "publicKey": "Public Key",
+        "publicKeyPlaceholder": "Paste SSH public key...",
+        "registryAddr": "Registry Address",
+        "registryPwdPlaceholder": "Registry password",
+        "certPem": "Certificate (PEM)",
+        "keyPem": "Private Key (PEM)",
+        "caCert": "CA Certificate",
+        "caCertPlaceholder": "CA certificate content...",
+        "dbType": "Database Type",
+        "host": "Host",
+        "dbName": "Database Name",
+        "dbPwdPlaceholder": "Database password",
+        "apiEndpoint": "API Endpoint",
+        "apiKeyToken": "API Key / Token",
+        "secretValuePlaceholder": "Secret value",
+        "saving": "Saving...",
+        "nameRequired": "Please enter credential name",
+        "updated": "Updated",
+        "created": "Created",
+        "operationFailed": "Operation failed",
+        "tagsLabel": "Tags"
+      }
     },
     "release": {
       "title": "Application Release",
@@ -2312,6 +2354,43 @@
       "decreaseReplica": "Decrease replicas",
       "increaseReplica": "Increase replicas",
       "noPod": "No Pods"
+    },
+    "compare": {
+      "title": "Multi-Cluster Resource Comparison",
+      "subtitle": "Cross-cluster resource usage, node distribution, health status comparison",
+      "clusterList": "Cluster List",
+      "noData": "No cluster data. Please add a Kubernetes cluster and sync first.",
+      "goAddCluster": "Add Cluster",
+      "resourceCompare": "Resource Count Comparison",
+      "usageCompare": "CPU / Memory Usage Comparison",
+      "radarCompare": "Resource Radar Comparison",
+      "nodeRoleDist": "Node Role Distribution",
+      "noNodeRoleData": "No node role data",
+      "detailCompare": "Detailed Comparison",
+      "clickRowHint": "Click a row to view cluster overview",
+      "loadFailed": "Failed to load",
+      "neverSynced": "Never synced",
+      "statusHealthy": "✓ Healthy",
+      "statusWarning": "⚠ Warning",
+      "statusError": "✗ Error",
+      "chartNodes": "Nodes",
+      "chartPods": "Pods",
+      "chartDeploy": "Deployments",
+      "chartCpuUsage": "CPU Usage",
+      "chartMemUsage": "Memory Usage",
+      "chartCpuCores": "CPU Cores",
+      "cpuPercent": "CPU %",
+      "memPercent": "Memory %",
+      "colCluster": "Cluster",
+      "colNodes": "Nodes",
+      "colCpuCores": "CPU Cores",
+      "colMemory": "Memory",
+      "colCpuUsage": "CPU Usage",
+      "colMemUsage": "Memory Usage",
+      "colRole": "Role",
+      "colSyncTime": "Sync Time",
+      "statCluster": "Clusters",
+      "statNodes": "Nodes"
     }
   },
   "monitor": {