Fix scheduler breaking DB encapsulation for one-time task disabling

Add Database.disable_task() public method and replace direct _conn
access in scheduler._run_due_tasks().

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cheddahbot/db.py

@@ -178,6 +178,13 @@ class Database:
         )
         self._conn.commit()
 
+    def disable_task(self, task_id: int):
+        """Disable a scheduled task (e.g. after a one-time task has run)."""
+        self._conn.execute(
+            "UPDATE scheduled_tasks SET enabled = 0 WHERE id = ?", (task_id,)
+        )
+        self._conn.commit()
+
     def log_task_run(self, task_id: int, result: str | None = None, error: str | None = None):
         now = _now()
         self._conn.execute(

cheddahbot/scheduler.py

@@ -97,10 +97,7 @@ class Scheduler:
                 schedule = task["schedule"]
                 if schedule.startswith("once:"):
                     # One-time task, disable it
-                    self.db._conn.execute(
-                        "UPDATE scheduled_tasks SET enabled = 0 WHERE id = ?", (task["id"],)
-                    )
-                    self.db._conn.commit()
+                    self.db.disable_task(task["id"])
                 else:
                     # Cron schedule - calculate next run
                     now = datetime.now(timezone.utc)