refactor(diagnostics): use model functions and clean up code

- Move all internal/local imports to top-level
- Remove unnecessary try-except blocks that just re-raise
- Replace direct Prisma count queries with get_graph_executions_count
- Add updated_time_gte/lte filter to get_graph_executions_count for
  querying failed/completed executions by update time
- Fix N+1 query in cleanup_orphaned_schedules_bulk by fetching all
  schedules once before the loop
- Extract SYSTEM_JOB_IDS constant to module level to avoid duplication

Co-authored-by: Nicholas Tindle <ntindle@users.noreply.github.com>

autogpt_platform/backend/backend/data/execution.py

@@ -546,6 +546,8 @@ async def get_graph_executions_count(
     created_time_lte: Optional[datetime] = None,
     started_time_gte: Optional[datetime] = None,
     started_time_lte: Optional[datetime] = None,
+    updated_time_gte: Optional[datetime] = None,
+    updated_time_lte: Optional[datetime] = None,
 ) -> int:
     """
     Get count of graph executions with optional filters.
@@ -558,6 +560,8 @@ async def get_graph_executions_count(
         created_time_lte: Optional maximum creation time
         started_time_gte: Optional minimum start time (when execution started running)
         started_time_lte: Optional maximum start time (when execution started running)
+        updated_time_gte: Optional minimum update time
+        updated_time_lte: Optional maximum update time
 
     Returns:
         Count of matching graph executions
@@ -584,6 +588,12 @@ async def get_graph_executions_count(
             "lte": started_time_lte or datetime.max.replace(tzinfo=timezone.utc),
         }
 
+    if updated_time_gte or updated_time_lte:
+        where_filter["updatedAt"] = {
+            "gte": updated_time_gte or datetime.min.replace(tzinfo=timezone.utc),
+            "lte": updated_time_lte or datetime.max.replace(tzinfo=timezone.utc),
+        }
+
     if statuses:
         where_filter["OR"] = [{"executionStatus": status} for status in statuses]