refactor: 简化报表中心状态展示并调整不可用文案

src/i18n/locales/en/reports.json

@@ -21,9 +21,7 @@
     "excel": "Excel"
   },
   "empty": "No matching reports",
-  "connected": "Connected",
-  "pending": "Pending",
-  "backendPending": "Backend API not connected yet",
+  "backendPending": "This report is temporarily unavailable",
   "filterPanel": "Filters",
   "queryHint": "Set filters and run a query to preview and export.",
   "query": "Query",
@@ -44,14 +42,14 @@
     "empty": "No data. Adjust filters and try again.",
     "exportableRows": "rows exportable",
     "columns": {
-      "primary": "Primary",
-      "secondary": "Secondary",
-      "metricA": "Metric A",
-      "metricB": "Metric B",
-      "metricC": "Metric C",
-      "status": "Status",
-      "extra": "Extra",
-      "time": "Time"
+      "primary": "",
+      "secondary": "",
+      "metricA": "",
+      "metricB": "",
+      "metricC": "",
+      "status": "",
+      "extra": "",
+      "time": ""
     },
     "stats": {
       "records": "Records",