refactor: change agent cloud data permission to cloud variables only

- Rename permission from '查看云端数据' to '查看云端变量'
- Remove cloud constants API and page for agents
- Add cloud variable records API for agents (stream type)
- Add agent cloud-variables page with full variable details
- Add agent cloud-variable records page (read-only)
- Update navigation from cloud-data to cloud-variables
- Update i18n keys: cloudData -> cloudVariables
- Backend returns var_type, default_value, max_records etc.
- Records page supports dynamic columns and date filtering

frontend/src/plugins/i18n/en.json

@@ -923,7 +923,7 @@
         "maxApiCalls": "API Calls/Month",
         "maxApiCallsPlaceholder": "-1 for unlimited",
         "allowAgent": "Agent Permission",
-        "allowCloudData": "Cloud Data",
+        "allowCloudData": "Cloud Variables",
         "allowDynamicCode": "Cloud Function",
         "allowEmail": "Email Feature",
         "allowExtension": "Extension API",
@@ -1286,7 +1286,7 @@
         "cardsCount": "Cards Generated",
         "childAgentsCount": "Child Agents",
         "canCreateAgent": "Create Agent Permission",
-        "canViewCloudData": "Cloud Data Permission",
+        "canViewCloudData": "View Cloud Variables Permission",
         "balance": "Balance",
         "createdAt": "Created At",
         "lastLoginAt": "Last Login"
@@ -2887,27 +2887,49 @@
         "generateNow": "Generate Now"
       }
     },
-    "cloudData": {
-      "title": "Cloud Data",
-      "description": "View cloud variables and constants (read-only)",
-      "variables": "Cloud Variables",
-      "constants": "Cloud Constants",
-      "applications": "Applications",
-      "dataList": "Data List",
-      "readOnlyHint": "Read-only mode, data cannot be edited",
-      "allApps": "All Applications",
+    "cloudVariables": {
+      "title": "Cloud Variables",
+      "description": "View cloud variables (read-only)",
+      "totalVariables": "Total Variables",
+      "appScopeVariables": "App Scope Variables",
+      "userScopeVariables": "User Scope Variables",
+      "appCount": "Applications",
       "noVariables": "No cloud variables found",
-      "noConstants": "No cloud constants found",
+      "appScope": "App",
+      "userScope": "User",
       "statusActive": "Active",
       "statusInactive": "Inactive",
-      "readOnlyNote": "Read-only - Data is for viewing only, no editing allowed",
+      "viewRecords": "View Records",
+      "application": "Application",
+      "scope": "Scope",
+      "types": {
+        "integer": "Integer",
+        "decimal": "Decimal",
+        "string": "String",
+        "binary": "Binary",
+        "stream": "Stream"
+      },
       "columns": {
-        "name": "Name",
-        "application": "Application",
+        "key": "Key",
+        "defaultValue": "Default Value",
+        "type": "Type",
         "scope": "Scope",
-        "value": "Value",
+        "application": "Application",
         "status": "Status",
         "createdAt": "Created At"
+      },
+      "records": {
+        "title": "Variable Records",
+        "description": "Records for variable {key}",
+        "totalRecords": "Total Records",
+        "maxRecordsLabel": "Max Records",
+        "unlimited": "Unlimited",
+        "user": "User",
+        "data": "Data",
+        "createdAt": "Created At",
+        "searchPlaceholder": "Search records...",
+        "startDate": "Start Date",
+        "endDate": "End Date"
       }
     }
   },
@@ -2932,7 +2954,7 @@
       "apiCalls": "{count} API calls/month",
       "unlimitedApiCalls": "Unlimited API calls",
       "agent": "Agent permission",
-      "cloudData": "Cloud data feature",
+      "cloudData": "Cloud Variables feature",
       "dynamicCode": "Dynamic code feature",
       "email": "Email feature",
       "extension": "Extension API",