Add Web Push notifications for backgrounded/frozen browser tabs

The SSE + in-page toast/sound system only works while the tab's JS is
actually running — Chrome (and other browsers) freeze a backgrounded
tab's JS after a stretch of inactivity to save power, so notifications
silently stop regardless of how correct the SSE/toast code is. A Service
Worker is the only mechanism that keeps receiving events independent of
the tab's own lifecycle, so this adds a real Web Push pipeline:

- New `push_subscriptions` table (one row per browser/device a user has
  subscribed from; endpoint is unique so re-subscribing overwrites
  rather than accumulating stale rows).
- VAPID keypair config (lib/push/vapid.ts) — reads
  VAPID_PUBLIC_KEY/VAPID_PRIVATE_KEY/VAPID_SUBJECT from the environment;
  push is silently disabled (never throws) if they're unset, matching
  this codebase's existing "an optional integration outage must never
  break the core flow" pattern (see the LDAP auth comment).
- public/sw.js: a minimal service worker — `push` -> showNotification,
  `notificationclick` -> focus or open the ticket.
- API routes: GET /api/push/vapid-public-key (client needs it to call
  pushManager.subscribe), POST/DELETE /api/push/subscribe.
- lib/push/client.ts: registers the service worker and subscribes,
  called from the notification bell after granting permission and again
  on mount for returning users who already granted it.
- lib/tickets/service.ts: appendMessage() now also fires a push (fire-
  and-forget, never awaited by the caller) to every admin plus the
  ticket's assignee whenever a *customer* message arrives — same "who
  should know" rule as the in-page toast (lib/tickets/visibility.ts).
  Failed sends are inspected: a 404/410 (push service no longer
  recognizes the subscription) prunes the row; anything else is just
  logged, since it might be transient.

Verified server-side end-to-end on this VM: saved a subscription via the
API, created a customer ticket, and confirmed the push attempt actually
fires (web-push validated and rejected a deliberately-malformed test
key, proving the send path is wired correctly) without blocking or
crashing ticket creation. Couldn't verify the full real-browser
subscribe-and-receive path or an actual OS popup from here — this VM has
no desktop/notification service, and headless Chromium's Notification
permission can't be reliably granted in this sandbox (unrelated to the
app code); that last mile needs verifying on a real machine.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012o9j9RezxbZVKQMrB7oRLY

src/lib/push/service.ts

@@ -0,0 +1,78 @@
+import { eq, inArray } from "drizzle-orm";
+import { db } from "@/lib/db/client";
+import { pushSubscriptions, users } from "@/lib/db/schema";
+import type { TicketDTO, MessageDTO } from "@/lib/tickets/types";
+import { webpush, ensureVapidConfigured } from "./vapid";
+
+export interface PushSubscriptionKeys {
+  endpoint: string;
+  keys: { p256dh: string; auth: string };
+}
+
+/** Re-subscribing from the same browser (e.g. after clearing site data and re-granting) overwrites the old row via the endpoint's unique constraint, rather than accumulating stale duplicates. */
+export async function savePushSubscription(userId: string, sub: PushSubscriptionKeys): Promise<void> {
+  await db
+    .insert(pushSubscriptions)
+    .values({ userId, endpoint: sub.endpoint, p256dh: sub.keys.p256dh, auth: sub.keys.auth })
+    .onConflictDoUpdate({
+      target: pushSubscriptions.endpoint,
+      set: { userId, p256dh: sub.keys.p256dh, auth: sub.keys.auth },
+    });
+}
+
+export async function deletePushSubscriptionByEndpoint(endpoint: string): Promise<void> {
+  await db.delete(pushSubscriptions).where(eq(pushSubscriptions.endpoint, endpoint));
+}
+
+async function sendPushToUsers(userIds: string[], payload: { title: string; body: string; url: string }): Promise<void> {
+  if (userIds.length === 0 || !ensureVapidConfigured()) return;
+
+  const subs = await db.query.pushSubscriptions.findMany({ where: inArray(pushSubscriptions.userId, userIds) });
+
+  await Promise.all(
+    subs.map(async (sub) => {
+      try {
+        await webpush.sendNotification(
+          { endpoint: sub.endpoint, keys: { p256dh: sub.p256dh, auth: sub.auth } },
+          JSON.stringify(payload),
+        );
+      } catch (err) {
+        // A 404/410 means the push service no longer recognizes this
+        // subscription (browser unsubscribed, site data cleared, endpoint
+        // expired) — prune it so future sends stop failing on it. Any other
+        // error (a transient network blip, ...) is left alone to retry on
+        // the next event rather than deleting a possibly-still-good row.
+        const statusCode = (err as { statusCode?: number }).statusCode;
+        if (statusCode === 404 || statusCode === 410) {
+          await db.delete(pushSubscriptions).where(eq(pushSubscriptions.endpoint, sub.endpoint));
+        } else {
+          console.error("[push] send failed for", sub.endpoint, err);
+        }
+      }
+    }),
+  );
+}
+
+/**
+ * Pushes to every admin plus the ticket's assignee (if any) — the same
+ * "who should know about this" set the in-page toast uses (see
+ * lib/tickets/visibility.ts), so a subscribed device is notified even while
+ * its browser tab is frozen in the background. Callers only invoke this for
+ * customer-authored messages; an agent's own reply or internal note is the
+ * agent's own action, not a signal anyone needs pushed to them.
+ */
+export async function notifyPushForCustomerMessage(
+  ticket: TicketDTO,
+  message: MessageDTO,
+  ticketIsNew: boolean,
+): Promise<void> {
+  const admins = await db.query.users.findMany({ where: eq(users.role, "admin") });
+  const userIds = new Set(admins.map((u) => u.id));
+  if (ticket.assigneeId) userIds.add(ticket.assigneeId);
+
+  await sendPushToUsers([...userIds], {
+    title: ticketIsNew ? "Новая заявка" : `Сообщение от ${message.authorName}`,
+    body: ticketIsNew ? ticket.subject : message.body.slice(0, 120),
+    url: `/tickets/${ticket.id}`,
+  });
+}