feat: web push notifications (VAPID)

- push_utils.py: subscription storage + send helper (auto-prunes 410 endpoints)
- routers/push.py: GET /api/push/vapid-key (public), POST/DELETE /api/push/subscribe
- sw.js: push event listener shows notification; notificationclick focuses/opens tab
- app.js: subscribe/unsubscribe flow + "Enable notifications" toggle in settings dropdown
- tools/notify.py: web_push orchestrator tool (user-level, no admin required)
- VAPID keys in .env; pywebpush added to requirements.txt

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

CLAUDE.md

@@ -226,12 +226,12 @@ Cortex is running and stable. All channels are live:
 
 Active users: scott (inara, developer), holly (tina), brian (wintermute)
 
-**39 orchestrator tools:** web_search, http_fetch,
+**40 orchestrator tools:** web_search, http_fetch,
 file_read/list/write, shell_exec, claude_allow_dir,
 cortex_restart/logs/status/update,
 task_list/create/update/complete, cron_list/add/remove/toggle,
 reminders_add/list/remove/clear, scratch_read/write/append/clear,
-email_send, nc_talk_send,
+web_push, email_send, nc_talk_send,
 ae_journal_list/search/entries_list/entry_read/entry_create/entry_update/entry_disable/entry_append/entry_prepend,
 ae_task_list.