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 tests for delete_bounties

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

Fixes #47

tests/test_services.py

@@ -210,6 +210,53 @@ class TestBountyService:
         result = self.service.delete_bounty(-1001, 999, self.admin_user_id)
         assert result is False
 
+    def test_delete_bounties_multiple_success(self):
+        """Test delete_bounties soft deletes multiple bounties."""
+        b1 = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="First"
+        )
+        b2 = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="Second"
+        )
+        b3 = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="Third"
+        )
+        results = self.service.delete_bounties(
+            -1001, [b1.id, b2.id, b3.id], self.admin_user_id
+        )
+        assert results == {b1.id: "deleted", b2.id: "deleted", b3.id: "deleted"}
+        assert self.service.get_bounty(-1001, b1.id) is None
+        assert self.service.get_bounty(-1001, b2.id) is None
+        assert self.service.get_bounty(-1001, b3.id) is None
+
+    def test_delete_bounties_mixed_results(self):
+        """Test delete_bounties returns individual results per ID."""
+        b1 = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="Exists"
+        )
+        results = self.service.delete_bounties(
+            -1001, [b1.id, 999, 888], self.admin_user_id
+        )
+        assert results == {b1.id: "deleted", 999: "not_found", 888: "not_found"}
+
+    def test_delete_bounties_permission_denied(self):
+        """Test delete_bounties returns permission_denied for non-admin."""
+        b1 = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="First"
+        )
+        b2 = self.service.add_bounty(
+            room_id=-1001, user_id=self.admin_user_id, text="Second"
+        )
+        results = self.service.delete_bounties(
+            -1001,
+            [b1.id, b2.id],
+            999,  # non-admin user
+        )
+        assert results == {b1.id: "permission_denied", b2.id: "permission_denied"}
+        # Bounties should not be deleted
+        assert self.service.get_bounty(-1001, b1.id) is not None
+        assert self.service.get_bounty(-1001, b2.id) is not None
+
 
 class TestTrackingService:
     """Unit tests for TrackingService."""