fix(push): fix VAPID key format and add regenerate endpoint + UI button

frontend/src/views/SettingsView.vue

@@ -428,6 +428,28 @@ const notifySecurityAlerts = ref(true);
 const savingNotifications = ref(false);
 const notificationsSaved = ref(false);
 
+// VAPID key reset (admin)
+const vapidResetting = ref(false);
+const vapidResetMsg = ref("");
+const vapidResetError = ref(false);
+
+async function resetVapidKeys() {
+  if (!confirm("This will regenerate VAPID keys and clear all push subscriptions. You will need to re-enable notifications afterwards. Continue?")) return;
+  vapidResetting.value = true;
+  vapidResetMsg.value = "";
+  vapidResetError.value = false;
+  try {
+    await apiPost("/api/push/reset-vapid", {});
+    vapidResetMsg.value = "Keys regenerated. Please re-enable notifications in this browser.";
+    pushStore.checkSubscription();
+  } catch {
+    vapidResetError.value = true;
+    vapidResetMsg.value = "Reset failed — check server logs.";
+  } finally {
+    vapidResetting.value = false;
+  }
+}
+
 // CalDAV settings (per-user)
 const caldav = ref({
   caldav_url: "",
@@ -1882,6 +1904,22 @@ function formatUserDate(iso: string): string {
             Notifications are blocked. Allow them in your browser site settings to re-enable.
           </p>
         </template>
+        <template v-if="authStore.isAdmin">
+          <div class="field-divider" style="margin: 1rem 0;" />
+          <p class="section-desc">
+            If push notifications fail due to a corrupted or misformatted VAPID key, regenerate
+            the key pair here. All existing subscriptions will be cleared — you will need to
+            re-enable notifications in this browser afterwards.
+          </p>
+          <div class="actions" style="margin-top: 0.5rem;">
+            <button class="btn-danger" :disabled="vapidResetting" @click="resetVapidKeys">
+              {{ vapidResetting ? 'Regenerating…' : 'Regenerate VAPID Keys' }}
+            </button>
+          </div>
+          <p v-if="vapidResetMsg" :class="vapidResetError ? 'field-error' : 'field-hint'" style="margin-top: 0.5rem;">
+            {{ vapidResetMsg }}
+          </p>
+        </template>
       </section>
 
       <section class="settings-section">