feat: login - passkey button under the password form, the sign-in button full width

internal/server/web/static/app.css

@@ -210,6 +210,7 @@ input.sw:disabled { opacity: .45; cursor: not-allowed; }
 /* Sign-in page. */
 .or { display: flex; align-items: center; gap: 10px; color: var(--muted); font-size: 13px; margin: 18px 0 4px; }
 .or::before, .or::after { content: ""; flex: 1; border-top: 1px solid var(--border); }
+.or + .keybtn { margin-top: 10px; }
 .keybtn { width: 100%; display: inline-flex; align-items: center; justify-content: center; gap: 8px; }
 
 /* Phones. A table marked .stack turns each row into a block of