refactor: improve code formatting and readability in configuration and run files

- Simplified the assignment of `bot_username` in `config.py` for better clarity.
- Removed redundant import statement in `run.py` to streamline the code.
- Enhanced formatting in `group_duty_pin.py` and test files for improved readability and consistency.
- No functional changes were made; the focus was on code style and organization.

duty_teller/handlers/group_duty_pin.py

@@ -439,7 +439,9 @@ async def trust_group_cmd(update: Update, context: ContextTypes.DEFAULT_TYPE) ->
     loop = asyncio.get_running_loop()
     already_trusted = await loop.run_in_executor(
         None,
-        lambda: _sync_trust_group(chat_id, update.effective_user.id if update.effective_user else None),
+        lambda: _sync_trust_group(
+            chat_id, update.effective_user.id if update.effective_user else None
+        ),
     )
     if already_trusted:
         await update.message.reply_text(t(lang, "trust_group.already_trusted"))