Auto-reload transactions after AI makes changes

When the AI updates a category (or any tool result), the transactions
page now automatically reloads. ChatPanel triggers a refresh counter
in the usePageContext composable when the response includes a tool
result, and TransactionsView watches that counter to reload data.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/composables/usePageContext.ts

@@ -1,6 +1,7 @@
 import { ref } from 'vue'
 
 const pageContext = ref('')
+const refreshTrigger = ref(0)
 
 export function usePageContext() {
   function setPageContext(context: string) {
@@ -11,5 +12,9 @@ export function usePageContext() {
     pageContext.value = ''
   }
 
-  return { pageContext, setPageContext, clearPageContext }
+  function triggerRefresh() {
+    refreshTrigger.value++
+  }
+
+  return { pageContext, setPageContext, clearPageContext, refreshTrigger, triggerRefresh }
 }