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.

webapp/js/constants.js

@@ -5,5 +5,3 @@
 export const FETCH_TIMEOUT_MS = 15000;
 export const RETRY_DELAY_MS = 800;
 export const RETRY_AFTER_ACCESS_DENIED_MS = 1200;
-
-export const THEME_BG = { dark: "#17212b", light: "#d5d6db" };