feat: enhance duty information handling with contact details and current duty view

- Added `bot_username` to settings for dynamic retrieval of the bot's username.
- Implemented `_resolve_bot_username` function to fetch the bot's username if not set, improving user experience in group chats.
- Updated `DutyWithUser` schema to include optional `phone` and `username` fields for enhanced duty information.
- Enhanced API responses to include contact details for users, ensuring better communication.
- Introduced a new current duty view in the web app, displaying active duty information along with contact options.
- Updated CSS styles for better presentation of contact information in duty cards.
- Added unit tests to verify the inclusion of contact details in API responses and the functionality of the current duty view.

duty_teller/db/schemas.py

@@ -55,13 +55,16 @@ class DutyInDb(DutyBase):
 
 
 class DutyWithUser(DutyInDb):
-    """Duty with full_name and event_type for calendar display.
+    """Duty with full_name, event_type, and optional contact fields for calendar display.
 
     event_type: only these values are returned; unknown DB values are mapped to "duty" in the API.
+    phone and username are exposed only to authenticated Mini App users (role-gated).
     """
 
     full_name: str
     event_type: Literal["duty", "unavailable", "vacation"] = "duty"
+    phone: str | None = None
+    username: str | None = None
 
     model_config = ConfigDict(from_attributes=True)