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>

package.json

@@ -21,7 +21,8 @@
     "db:migrate": "drizzle-kit migrate",
     "db:seed": "tsx --env-file=.env scripts/seed.ts",
     "db:studio": "drizzle-kit studio",
-    "gen:icons": "node scripts/generate-icons.mjs"
+    "gen:icons": "node scripts/generate-icons.mjs",
+    "vapid:generate": "node scripts/vapid-generate.mjs"
   },
   "devDependencies": {
     "@eslint/eslintrc": "^3.3.5",
@@ -32,6 +33,7 @@
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
     "@types/react-grid-layout": "^2.1.0",
+    "@types/web-push": "^3.6.4",
     "drizzle-kit": "^0.31.10",
     "eslint": "^9.15.0",
     "eslint-config-next": "^16.2.4",
@@ -64,6 +66,7 @@
     "shadcn": "^4.7.0",
     "tailwind-merge": "^3.5.0",
     "tw-animate-css": "^1.4.0",
+    "web-push": "^3.6.7",
     "zod": "^4.4.3",
     "zod-to-json-schema": "^3.25.2"
   }