Add voice bot welcome tracking functionality

- Implemented methods to check and mark if a user has received a welcome message from the voice bot in both async and synchronous database classes.
- Updated database schema to include a new field for tracking welcome message status.
- Enhanced voice handler to utilize the new tracking methods, improving user interaction flow and engagement metrics.

database/schema.sql

@@ -86,7 +86,8 @@ CREATE TABLE IF NOT EXISTS our_users (
     has_stickers INTEGER DEFAULT 0 NOT NULL,
     emoji TEXT,
     date_added DATE NOT NULL,
-    date_changed DATE NOT NULL
+    date_changed DATE NOT NULL,
+    voice_bot_welcome_received BOOLEAN DEFAULT 0
 );
 
 -- Audio moderation tracking