The 24h session cap from the M-2 audit finding was hard-coded, so the
"Remember Me" checkbox could only control storage location, never
duration. Add session_max_hours setting (default 24, max 720) honoured
at all four token-issuance sites: plain login, 2FA TOTP/email, 2FA
backup, OIDC.
- backend/app/core/auth.py: SESSION_MAX_HOURS_HARD_CEILING + resolver
that clamps to [1h, 720h] and falls back to 24h on missing/blank/
unparseable. DB errors propagate — the login transaction must abort
on a broken DB rather than silently extend or shrink the lifetime.
- backend/app/api/routes/auth.py, mfa.py: all four sites read the
resolved value instead of ACCESS_TOKEN_EXPIRE_MINUTES directly.
- backend/app/schemas/settings.py, routes/settings.py: schema field
with ge=1 le=720 + int coercion in _build_settings_response.
- frontend/src/pages/SettingsPage.tsx: half-width card at top of
Settings -> Users left column with 24h/7d/30d presets, custom input,
and a yellow warning when value > 24h.
- frontend/src/i18n/locales/*.ts: 8 new keys per locale, real
translations in all 11 (en/de/es/fr/it/ja/ko/pt-BR/tr/zh-CN/zh-TW).
- backend/tests/integration/test_session_policy.py: 15 tests across
resolver clamping, login JWT exp end-to-end, settings API round-trip.
Already-issued tokens keep their original expiry; the new setting only
affects future logins.
