refactor(variable): update global variable names and types for consistency

web/app/components/workflow/constants.ts

@@ -70,8 +70,8 @@ export const getGlobalVars = (isChatMode: boolean): Var[] => {
     },
     ...((isInWorkflow && !isChatMode) ? [
       {
-        variable: 'sys.trigger_timestamp',
-        type: VarType.string,
+        variable: 'sys.timestamp',
+        type: VarType.integer,
       },
     ] : []),
   ]

web/app/components/workflow/panel/global-variable-panel/index.tsx

@@ -51,8 +51,8 @@ const Panel = () => {
     },
     // is workflow
     ...((isWorkflowPage && !isChatMode) ? [{
-      name: 'trigger_timestamp',
-      value_type: 'string' as const,
+      name: 'timestamp',
+      value_type: 'integer' as const,
       description: t('workflow.globalVar.fieldsDescription.triggerTimestamp'),
     }] : []),
   ]