Add the speaker group to the microphone menu

The chevron beside the microphone button now opens a menu headed "Audio
controls" that lists the microphones and, below a separator, the audio
outputs. Selecting either switches the device and keeps the menu open.
Where the browser offers no choice of output, or only one, the speaker
group still names the output in use as a non-selectable row.

The footer view model derives the outputs from the same MediaDevices
helper as the device lists, so the menu reaches both surfaces at once:
in a call on desktop, and before joining on every platform.

Spec: FEATURES_SPEC/2026-09_Audio_Quick_Menu.md, slice 1 — AC1, AC2, AC3,
AC5, AC6, AC7, AC25.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

locales/en/app.json

@@ -23,6 +23,9 @@
     "upload_file": "Upload file"
   },
   "analytics_notice": "By participating in this beta, you consent to the collection of anonymous data, which we use to improve the product. You can find more information about which data we track in our <2>Privacy Policy</2> and our <6>Cookie Policy</6>.",
+  "audio_menu": {
+    "title": "Audio controls"
+  },
   "call_ended_view": {
     "create_account_button": "Create account",
     "create_account_prompt": "<0>Why not finish by setting up a password to keep your account?</0><1>You'll be able to keep your name and set an avatar for use on future calls</1>",