Let streamers name their AI assistant; fix overlay TTS audio overlap

Streamer dashboard gains an editable AI assistant name (default
"Альтушка Ирина"), stored per-streamer and used for the overlay label,
TTS intro, and DeepSeek system prompt. Also fixes a bug where a long
message's TTS audio could still be playing when the next queued
message started its own audio — the overlay queue now waits for the
current audio to actually finish (not just the configured display
duration) before advancing.

db.js

@@ -19,6 +19,7 @@ db.exec(`
     sender_token TEXT UNIQUE NOT NULL,
     tts_voice TEXT NOT NULL DEFAULT 'ru-RU-DmitryNeural',
     display_duration_seconds INTEGER NOT NULL DEFAULT 10,
+    ai_name TEXT NOT NULL DEFAULT 'Альтушка Ирина',
     created_at INTEGER NOT NULL
   );
 
@@ -36,6 +37,9 @@ const existingColumns = db.prepare('PRAGMA table_info(streamers)').all().map((c)
 if (!existingColumns.includes('display_duration_seconds')) {
   db.exec('ALTER TABLE streamers ADD COLUMN display_duration_seconds INTEGER NOT NULL DEFAULT 10');
 }
+if (!existingColumns.includes('ai_name')) {
+  db.exec("ALTER TABLE streamers ADD COLUMN ai_name TEXT NOT NULL DEFAULT 'Альтушка Ирина'");
+}
 
 function generateToken() {
   return crypto.randomBytes(16).toString('hex');
@@ -86,6 +90,10 @@ function updateDisplayDuration(streamerId, seconds) {
   db.prepare('UPDATE streamers SET display_duration_seconds = ? WHERE id = ?').run(seconds, streamerId);
 }
 
+function updateAiName(streamerId, aiName) {
+  db.prepare('UPDATE streamers SET ai_name = ? WHERE id = ?').run(aiName, streamerId);
+}
+
 module.exports = {
   findStreamerByOverlayToken,
   findStreamerBySenderToken,
@@ -93,4 +101,5 @@ module.exports = {
   getViewerName,
   setViewerName,
   updateDisplayDuration,
+  updateAiName,
 };