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/functions/backend/db/bots/grab-speakable-message.ts

@@ -0,0 +1,37 @@
+import BunSQLite from "@moduletrace/bun-sqlite";
+import type { BUN_SQLITE_COBBLE_BOT_MESSAGES } from "@/db/types/db";
+import AppError from "@/src/utils/app-error";
+import grabUserConversation from "../bot-sessions/grab-user-conversation";
+
+type Params = {
+    user_id: number;
+    message_id: number;
+};
+
+/**
+ * A bot message in one of the user's own sessions, for reading aloud,
+ * with the conversation it's in (so a lost grant blocks it). Throws when
+ * it isn't theirs.
+ */
+export default async function grabSpeakableMessage({ user_id, message_id }: Params) {
+    const message = (
+        await BunSQLite.sql<BUN_SQLITE_COBBLE_BOT_MESSAGES>({
+            sql: `SELECT m.* FROM bot_messages m
+                JOIN bot_sessions s ON s.id = m.session_id
+                WHERE m.id = ? AND m.author = 'bot' AND s.user_id = ?`,
+            values: [message_id, user_id],
+        })
+    ).payload?.[0];
+
+    if (!message?.id || !message.bot_id) {
+        throw new AppError(`Message not found`);
+    }
+
+    const conversation = await grabUserConversation({
+        user_id,
+        bot_id: message.bot_id,
+        workspace_id: message.workspace_id || null,
+    });
+
+    return { message, conversation };
+}