Deletes the session row keyed by the cookie/bearer token and
clears the cookie on the client. Best-effort DB delete — logout
still succeeds for the client if the row's already gone.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Verifies bcrypt password hash, mints a session token, stores its
sha256 in the sessions table, and returns the token in both the
response body (for Flutter) and an httpOnly/SameSite=Strict
cookie (for the web SPA).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>