feat(autofill): Ctrl+Shift+T types the 2FA code

Same workflow as the password-only hotkey: click the 2FA field, press the
combo, the current 6-digit code is typed in.

Reuses the whole autofill pipeline — no new native typing path. The code is
sent in the password slot with an empty username, so Delphi's existing
password-only branch types just the code.

- Bridge: akTotp kind, hotkey id 47, registered/torn down alongside the other
  two autofill combos; an unconfigured combo (vk=0) doesn't count as a
  registration failure.
- Matching filters on totp_secret BEFORE scoring, so the multi-match picker
  never offers an entry that has no code.
- Configurable + synced like the others (autofillHotkeyTotp), collision-checked
  against the other four slots, covered by Reset to defaults and the cheatsheet.

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

index.html

@@ -675,6 +675,12 @@
                         </span>
                         <button class="btn btn-ghost btn-sm hotkey-capture-btn" id="settingAutofillPwdCombo">Ctrl+Shift+P</button>
                     </div>
+                    <div class="setting-row">
+                        <span style="font-size:12px;color:var(--text-dim)">
+                            2FA code only (click the 2FA field first)
+                        </span>
+                        <button class="btn btn-ghost btn-sm hotkey-capture-btn" id="settingAutofillTotpCombo">Ctrl+Shift+T</button>
+                    </div>
                     <div class="setting-row">
                         <span style="font-size:12px;color:var(--text-dim)">
                             Quick search picker (find entry, fill from anywhere)