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/schemas/bot-schema.ts

@@ -107,3 +107,20 @@ export const UploadBotAttachmentRequestSchema = z.object({
 });
 
 export type UploadBotAttachmentRequest = z.infer<typeof UploadBotAttachmentRequestSchema>;
+
+export const TranscribeVoiceRequestSchema = z.object({
+    bot_id: z.coerce.number().int().positive("Pick a bot"),
+    workspace_id: WorkspaceIdField,
+    /**
+     * The recording as a base64 data URL.
+     */
+    data_url: z.string().startsWith("data:audio/", "Send the recording as an audio data URL"),
+});
+
+export type TranscribeVoiceRequest = z.infer<typeof TranscribeVoiceRequestSchema>;
+
+export const SpeakBotMessageRequestSchema = z.object({
+    message_id: z.coerce.number().int().positive("Pick a message"),
+});
+
+export type SpeakBotMessageRequest = z.infer<typeof SpeakBotMessageRequestSchema>;