fix: address audit findings for websearch and balance notification

- Fix GetByKeyForAuth not selecting balance notify fields (notifications
  never triggered in gateway path)
- Fix provider-level ProxyURL never resolved: inject ProxyRepository into
  SettingService, resolve proxy URLs when building Manager
- Fix admin manual balance adjustment not updating total_recharged
- Add threshold_type input validation (reject invalid values)
- Fix user threshold_type inheritance: custom threshold defaults to "fixed"
  instead of inheriting global type (prevents $5 being treated as 5%)
- Add try-catch for clipboard.writeText (fails on non-HTTPS)
- Add SetTotalRecharged to user Update for admin balance operations

frontend/src/views/admin/SettingsView.vue

@@ -3109,8 +3109,12 @@ async function copyApiKey(idx: number) {
     appStore.showError(t('admin.settings.webSearchEmulation.apiKeyPlaceholder'))
     return
   }
-  await navigator.clipboard.writeText(key)
-  appStore.showSuccess(t('admin.settings.webSearchEmulation.copied'))
+  try {
+    await navigator.clipboard.writeText(key)
+    appStore.showSuccess(t('admin.settings.webSearchEmulation.copied'))
+  } catch {
+    appStore.showError(t('common.error'))
+  }
 }
 
 async function testWebSearchProvider() {