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>

js/app.overlays.js

@@ -187,6 +187,7 @@ const CHEATSHEET_GROUPS = [
         items: [
             { keys: ['Ctrl', 'Shift', 'L'], desc: 'Autofill username + password into the active window' },
             { keys: ['Ctrl', 'Shift', 'P'], desc: 'Autofill password only (step-2 forms, unlock screens)' },
+            { keys: ['Ctrl', 'Shift', 'T'], desc: 'Autofill the 2FA code (click the 2FA field first)' },
             { keys: ['Ctrl', 'Shift', 'Q'], desc: 'Quick search → SendInput password into the active window' },
             { keys: ['Ctrl', 'Shift', 'A'], desc: 'Quick-add a new entry pre-filled with the foreground window title' },
         ],