feat: add group duty pin notification feature

- Introduced a new configuration option `DUTY_PIN_NOTIFY` to control whether the bot re-pins the duty message when updated, providing notifications to group members.
- Updated the architecture documentation to reflect the new functionality of re-pinning duty messages.
- Enhanced the `.env.example` file to include the new configuration option with a description.
- Added tests to verify the behavior of the new refresh pin command and its integration with the existing group duty pin functionality.
- Updated internationalization messages to include help text for the new `/refresh_pin` command.

duty_teller/handlers/commands.py

@@ -163,6 +163,7 @@ async def help_cmd(update: Update, context: ContextTypes.DEFAULT_TYPE) -> None:
         t(lang, "help.set_phone"),
         t(lang, "help.calendar_link"),
         t(lang, "help.pin_duty"),
+        t(lang, "help.refresh_pin"),
     ]
     if await is_admin_async(update.effective_user.id):
         lines.append(t(lang, "help.import_schedule"))