bbefe91011
Add UserService.BumpLoginEpoch and call it from updateSetting when
TwoFactorEnable flips false → true. Existing cookies (issued under
the looser no-2FA policy) get a 401 on their next request and are
forced through the login flow. Disabling 2FA is a relaxation and
does not bump the epoch — sessions stay valid.
Also fix the dev-mode 401 redirect: targeting `${basePath}login.html`
breaks when basePath isn't "/" (Vite has no file at e.g.
"/test/login.html"; the SPA fallback loops the 401). Navigate to
basePath instead — Vite's bypassMigratedRoute and Go's index
handler both serve login.html for that path.
Strip stale doc-comment from netsafe and IndexController.logout
in line with the project's no-inline-comments convention.