feat(settings): fixed-height modal + move unlock sections to Account

- Centered settings modal gets a fixed height (min(88vh,620px)) so switching
  between short/long tabs no longer resizes + re-centers it. Entry #slideover
  stays content-sized (edit/new unaffected).
- PIN unlock / Quick unlock / Recovery key moved from Sécurité to the Account
  tab (unlock methods live with the account). Autofill stays in Sécurité.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

css/style.css

@@ -2112,6 +2112,10 @@ body[data-editor-position="center"] #settingsPanel {
     pointer-events: none;
     transition: transform var(--t-base), opacity var(--t-base);
 }
+/* Settings gets a FIXED height in centered mode so switching tabs (short vs
+   long) doesn't resize + re-center the modal. Entry #slideover stays
+   content-sized (grows with the form). */
+body[data-editor-position="center"] #settingsPanel { height: min(88vh, 620px); }
 body[data-editor-position="center"] #slideover.is-open,
 body[data-editor-position="center"] #settingsPanel.is-open {
     transform: translate(-50%, -50%) scale(1);