Add dictation and streamed read-aloud to the chat

- A mic in the composer records, transcribes with the bot's
  transcription model (api/admin/bots/transcribe) and writes the text
  into the input at the cursor to edit before sending. Escape cancels;
  recordings aren't stored.
- Every bot message has a read-aloud button that plays
  GET api/admin/bots/speak-message, streamed from the provider as the
  audio is made, so it starts in a couple of seconds. One message plays
  at a time; only the user's own sessions can be read.
- Both buttons stay visible but disabled while the bot has no model for
  them (bot_voice page prop).
- Transcription and speech no longer pick free models automatically:
  they're not available until a model is picked, and Settings says so.
  Transcription lists speech-to-text models only, so the chat-model
  transcript path and its missing-audio check are gone.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/utils/speech-text.ts

@@ -0,0 +1,16 @@
+import { AppData } from "@/src/data/app-data";
+import messagePreview from "./message-preview";
+
+/**
+ * A bot message as text to read aloud: plain text (`messagePreview`),
+ * take-over refs as "a take-over link", cut at `AppData.SpeechMaxChars`.
+ */
+export default function speechText({ text }: { text: string }) {
+    const plain = messagePreview({
+        text: text.replace(/\[take-over:\d+:[a-z]+\](?!\()/g, "a take-over link"),
+    });
+
+    if (plain.length <= AppData.SpeechMaxChars) return plain;
+
+    return `${plain.slice(0, AppData.SpeechMaxChars).trimEnd()}…`;
+}