Plan for update button

docs/plan.md

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+### Backlog — Manual "Check for updates" button in Settings
+
+**Status:** 🔲 To do — not yet planned in detail, not implemented
+
+**Requested:** 2026-07-21, user request — the PWA doesn't seem to update automatically; add a manual update button in Settings.
+
+**Why:** Step 24 (`useAppUpdate.js`, `AppUpdateDialog.vue`) already shows an update prompt when the browser detects a new service worker, but that detection only runs on the browser's own schedule (roughly on navigation/reload) — if the PWA is left open, an update can go unnoticed for a long time. A manual trigger in Settings lets the user force a check on demand.
+
+**Discussed approach (not yet implemented):**
+
+- `useAppUpdate.js` — capture the SW `registration` via `useRegisterSW`'s `onRegisteredSW` callback; add `checkForUpdate()` that calls `registration.update()` to force the browser to re-fetch the SW script. If it changed, the existing `needRefresh` flow fires and `AppUpdateDialog` appears as usual (same "Update now" / "Later" choice — user retains the option to defer even when an update is found).
+- `SettingsView.vue` — new "Application" card: a "Check for updates" button, with a brief inline status message ("You're up to date") shown for a few seconds when a check finds nothing (via a timeout heuristic, since there's no direct "no update" event from the SW API).
+- Explicitly out of scope: no periodic/background auto-check — checking stays a deliberate user action, and updating stays optional even when available (user decision 2026-07-21).
+
+**Not started:** no code, no tests, no i18n keys yet.
+
+---
+
 ## Data Model
 
 ```mermaid