feat(web): voice input — record, check the recognised text, send

Microphone button in the chat composer and in free-text steps. The browser
records 16 kHz mono WAV (no server-side ffmpeg), /me/{token}/stt transcribes,
the text lands in the field for the patient to check and edit — never sent
automatically, so safety and scrub() apply on send. Hidden when the server has
voice input off or the browser lacks a microphone API. nginx: 4 MB body limit.

Refs #117

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/screens/Messages.tsx

@@ -3,6 +3,7 @@ import { useNavigate } from "react-router-dom";
 
 import { AppShell, TopBar } from "../components/AppShell";
 import { Icon } from "../components/Icon";
+import { VoiceInput } from "../components/VoiceInput";
 import { ru } from "../content/ru";
 import { useDialog } from "../dialog/DialogContext";
 
@@ -112,6 +113,11 @@ export function Messages() {
             onKeyDown={onKeyDown}
             maxLength={2000}
           />
+          <VoiceInput
+            compact
+            disabled={dialog.busy}
+            onText={(text) => setDraft((prev) => (prev.trim() ? `${prev.trim()} ${text}` : text).slice(0, 2000))}
+          />
           <button type="submit" className="send" disabled={dialog.busy || !draft.trim()} aria-label={ru.common.send}>
             <Icon name="send" size={20} />
           </button>