Address PR #19 review feedback: simplify models

- Remove GroupBounty/PersonalBounty subclasses, use Bounty with optional created_by_user_id
- Combine UserData/GroupData into RoomData with room_id and is_group fields
- Add group_id field to TrackingData (supports negative Telegram group IDs)
- Add test_bounty_comparison_not_equal for verifying different bounties are not equal
- Update core/__init__.py exports

core/models.py

@@ -6,27 +6,18 @@ from typing import Optional
 
 @dataclass
 class Bounty:
-    """Base bounty with common fields."""
+    """Bounty - used for both group and personal bounties.
+
+    Use created_by_user_id to distinguish: if set, it's a group bounty
+    created by that user. If None, it's a personal/DM bounty.
+    """
 
     id: int
     text: Optional[str]
     link: Optional[str]
     due_date_ts: Optional[int]
     created_at: int
-
-
-@dataclass
-class GroupBounty(Bounty):
-    """Bounty created in a group context."""
-
-    created_by_user_id: int
-
-
-@dataclass
-class PersonalBounty(Bounty):
-    """Bounty created in DM/personal context."""
-
-    pass
+    created_by_user_id: Optional[int] = None
 
 
 @dataclass
@@ -38,26 +29,27 @@ class TrackedBounty:
 
 
 @dataclass
-class GroupData:
-    """All data for a group."""
+class RoomData:
+    """All data for a room (group or DM).
 
-    group_id: int
-    bounties: list[GroupBounty]
+    For groups: is_group=True, room_id is negative (Telegram group ID)
+    For DMs: is_group=False, room_id is the user_id (positive)
+    next_id is used to generate unique bounty IDs within this room.
+    """
+
+    room_id: int
+    is_group: bool
+    bounties: list[Bounty]
     next_id: int
 
 
 @dataclass
 class TrackingData:
-    """User tracking data within a group."""
+    """User tracking data within a group.
 
+    group_id is the Telegram group ID (always negative).
+    """
+
+    group_id: int
     user_id: int
     tracked: list[TrackedBounty]
-
-
-@dataclass
-class UserData:
-    """All personal bounties for a user (DM mode)."""
-
-    user_id: int
-    bounties: list[PersonalBounty]
-    next_id: int