Refactor job pkg errors

internal/job/job.go

@@ -108,16 +108,16 @@ func New(
 		return nil, fmt.Errorf("invalid config: %w", err)
 	}
 	if db == nil {
-		return nil, fmt.Errorf("database is nil")
+		return nil, fmt.Errorf("missing database")
 	}
 	if llmc == nil {
-		return nil, fmt.Errorf("llm client is nil")
+		return nil, fmt.Errorf("missing llm client")
 	}
 	if log == nil {
-		return nil, fmt.Errorf("logger is nil")
+		return nil, fmt.Errorf("missing logger")
 	}
 	if tools == nil {
-		return nil, fmt.Errorf("tools registry is nil")
+		return nil, fmt.Errorf("missing tool registry")
 	}
 
 	sched, err := cron.ParseStandard(cfg.Schedule)