Implement tasks 40, 41, 42: web push, notification bus, reminders engine

Task 40 — Web Push (VAPID):
- Add web-push package + @types/web-push
- pnpm vapid:generate script prints VAPID_PUBLIC_KEY, VAPID_PRIVATE_KEY, NEXT_PUBLIC_VAPID_PUBLIC_KEY
- push_subscriptions schema + migration 0013
- _core/push.ts: sendPush() iterates subscriptions, prunes 404/410 stale entries
- SW push/notificationclick event handlers added to generated sw.js template
- PushOptIn client component on /settings (opt-in, disable, send test)

Task 42 — Notification bus + ntfy adapter:
- notifications table + notif_push/notif_inapp/notif_ntfy user columns (migration 0013)
- _core/notify.ts: notify() fans out to push, in-app DB, and optional ntfy POST
- NotificationBell server component in AppNav: unread badge, dropdown inbox, mark-read
- NotifyChannelToggles client component in /settings

Task 41 — Reminders engine:
- fired_at + created_by added to reminders; default channel changed to 'auto'
- _core/reminders.ts: scheduleReminder (upsert), cancelReminder, listReminders, tickReminders
- tickReminders uses pg_try_advisory_xact_lock for horizontal-scale safety
- src/instrumentation.ts starts reminder worker (30s tick) on Node.js boot
- Notes actions use scheduleReminder/cancelReminder instead of raw SQL
- Calendar createEvent: optional remindMinutesBefore, deleteEvent: cancelReminder
- Calendar-shell: "Remind me 30 min before" checkbox on new event form

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

src/components/push-opt-in.tsx

@@ -0,0 +1,92 @@
+"use client";
+
+import { useState, useTransition } from "react";
+import { Button } from "@/components/ui/button";
+import { subscribeToPush, unsubscribeFromPush, sendTestNotification } from "@/app/settings/push-actions";
+
+const VAPID_KEY = process.env.NEXT_PUBLIC_VAPID_PUBLIC_KEY ?? "";
+
+function urlBase64ToUint8Array(base64String: string): Uint8Array<ArrayBuffer> {
+  const padding = "=".repeat((4 - (base64String.length % 4)) % 4);
+  const base64 = (base64String + padding).replace(/-/g, "+").replace(/_/g, "/");
+  const raw = atob(base64);
+  const buf = new Uint8Array(raw.length);
+  for (let i = 0; i < raw.length; i++) buf[i] = raw.charCodeAt(i);
+  return buf;
+}
+
+export function PushOptIn() {
+  const [status, setStatus] = useState<"idle" | "subscribed" | "denied" | "unsupported">(
+    "idle",
+  );
+  const [endpoint, setEndpoint] = useState<string | null>(null);
+  const [isPending, startTransition] = useTransition();
+  const [testSent, setTestSent] = useState(false);
+
+  if (!VAPID_KEY) return null;
+  if (!("serviceWorker" in navigator) || !("PushManager" in window)) {
+    return <p className="text-sm text-muted-foreground">Push notifications not supported in this browser.</p>;
+  }
+
+  async function subscribe() {
+    try {
+      const registration = await navigator.serviceWorker.ready;
+      const sub = await registration.pushManager.subscribe({
+        userVisibleOnly: true,
+        applicationServerKey: urlBase64ToUint8Array(VAPID_KEY),
+      });
+      const json = sub.toJSON() as { endpoint: string; keys: { p256dh: string; auth: string } };
+      startTransition(async () => {
+        await subscribeToPush(json, navigator.userAgent);
+        setEndpoint(json.endpoint);
+        setStatus("subscribed");
+      });
+    } catch {
+      setStatus("denied");
+    }
+  }
+
+  async function unsubscribe() {
+    if (!endpoint) return;
+    const registration = await navigator.serviceWorker.ready;
+    const sub = await registration.pushManager.getSubscription();
+    if (sub) await sub.unsubscribe();
+    startTransition(async () => {
+      await unsubscribeFromPush(endpoint);
+      setEndpoint(null);
+      setStatus("idle");
+    });
+  }
+
+  function sendTest() {
+    startTransition(async () => {
+      await sendTestNotification();
+      setTestSent(true);
+      setTimeout(() => setTestSent(false), 3000);
+    });
+  }
+
+  if (status === "denied") {
+    return <p className="text-sm text-destructive">Notification permission denied. Enable it in browser settings.</p>;
+  }
+
+  if (status === "subscribed") {
+    return (
+      <div className="flex items-center gap-3">
+        <span className="text-sm text-green-600 dark:text-green-400">Push notifications enabled</span>
+        <Button size="sm" variant="outline" onClick={sendTest} disabled={isPending}>
+          {testSent ? "Sent!" : "Send test"}
+        </Button>
+        <Button size="sm" variant="destructive" onClick={unsubscribe} disabled={isPending}>
+          Disable
+        </Button>
+      </div>
+    );
+  }
+
+  return (
+    <Button size="sm" onClick={subscribe} disabled={isPending}>
+      Enable push notifications
+    </Button>
+  );
+}