feat: add multi-ID delete support with per-ID results

- Add delete_bounties() method to BountyService that returns individual
  results per bounty ID (deleted, not_found, permission_denied)
- Update cmd_delete to accept multiple IDs and show per-ID messages
- Add 3 tests for delete_bounties method

Example output:
/delete 1 2 3
✅ Bounty #1 deleted.
✅ Bounty #2 deleted.
⛔ Bounty #3 not found.

Fixes #47

tests/test_services.py

@@ -210,6 +210,46 @@ class TestBountyService:
         result = self.service.delete_bounty(-1001, 999, self.admin_user_id)
         assert result is False
 
+    def test_delete_bounties_multi_id_success(self):
+        """Test delete_bounties returns individual results for multiple bounties."""
+        bounty1 = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="To delete 1"
+        )
+        bounty2 = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="To delete 2"
+        )
+        results = self.service.delete_bounties(
+            -1001, [bounty1.id, bounty2.id], self.admin_user_id
+        )
+        assert results == {bounty1.id: "deleted", bounty2.id: "deleted"}
+        # Verify both are soft deleted
+        assert self.service.get_bounty(-1001, bounty1.id) is None
+        assert self.service.get_bounty(-1001, bounty2.id) is None
+
+    def test_delete_bounties_mixed_results(self):
+        """Test delete_bounties returns not_found for non-existent bounties."""
+        bounty = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="To delete"
+        )
+        results = self.service.delete_bounties(
+            -1001, [bounty.id, 999, 888], self.admin_user_id
+        )
+        assert results == {bounty.id: "deleted", 999: "not_found", 888: "not_found"}
+
+    def test_delete_bounties_permission_denied(self):
+        """Test delete_bounties returns permission_denied for non-admin users."""
+        bounty = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="To delete"
+        )
+        results = self.service.delete_bounties(
+            -1001,
+            [bounty.id],
+            999,  # non-admin user
+        )
+        assert results == {bounty.id: "permission_denied"}
+        # Verify bounty was NOT deleted
+        assert self.service.get_bounty(-1001, bounty.id) is not None
+
 
 class TestTrackingService:
     """Unit tests for TrackingService."""