Keep session alive during active typing/reading, warn before expiry

[apodacaduron]

Description

Sessions were expiring mid-sentence. Idle timeout only slid forward on
HTTP requests, so typing or scrolling (no requests sent) looked idle and
users got logged out mid-form.

Adds a global session controller, mixed into all admin pages:

• Tracks real interaction (keydown, input, pointerdown, wheel, touchmove)
  and pings /admin/api/session-check on a cadence based on the session
  lifetime. Programmatic scroll doesn't count, only wheel/touchmove.
• Shows a 60s countdown with "Stay signed in" before actual expiry.
  Only clicking it extends the session.
• Uses localStorage so multiple tabs share one keepalive and only the
  active tab shows the warning.
• Also fixes: split-view tabs never fire visibilitychange on each other,
  so a stale "Session Expired" dialog in tab B wouldn't close after
  signing in on tab A. Sign-in now broadcasts to sibling tabs.

Frontend only, no API/DB changes. Exposes the existing
PERMANENT_SESSION_LIFETIME via one Jinja attribute. Notification poller
(#343) untouched.

Not included: request recovery after expiry, draft autosave.

How to Test

Set SESSION_LIFETIME=120 in .env, restart, revert before merge.

• Type on and off for 3-4 min: no logout, one keepalive every ~40s
• Scroll a long record with trackpad only, no keyboard: no logout
• Type then stop: warning shows around 1 min left, expires if ignored
• Click "Stay signed in": dialog closes, timer resets
• 5 tabs, use one: only that tab warns and pings
• Split view, both expired, sign in on one: other tab closes on its own
• Sleep past expiry, wake: no stale countdown
• window.scrollTo() from console with no real input: no keepalive

Jira ID (if applicable)

BYNT-1763

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 46d9100b-674c-41ca-bbe5-89378a6c8d66

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}