Feat: add built in DSL file API (#17003)

### Summary

1. list and get by id API for builtin DSL
2. add DSL default component param values validation
3. remove all hard code keys for parser config

internal/handler/error_test.go

@@ -0,0 +1,43 @@
+package handler
+
+import (
+	"testing"
+
+	"ragflow/internal/common"
+	"ragflow/internal/service"
+)
+
+func TestIngestionTaskErrorCode(t *testing.T) {
+	testCases := []struct {
+		name string
+		err  error
+		want common.ErrorCode
+	}{
+		{
+			name: "invalid transition",
+			err:  &service.InvalidTaskTransitionError{TaskID: "task-1", From: common.CREATED, To: common.COMPLETED},
+			want: common.CodeConflict,
+		},
+		{
+			name: "status conflict",
+			err:  &service.TaskStatusConflictError{TaskID: "task-1", ExpectedFrom: common.CREATED, AttemptedTo: common.RUNNING, ActualCurrent: common.STOPPING},
+			want: common.CodeConflict,
+		},
+		{
+			name: "task not found",
+			err:  common.ErrTaskNotFound,
+			want: common.CodeNotFound,
+		},
+		{
+			name: "fallback",
+			err:  common.ErrInvalidToken,
+			want: common.CodeExceptionError,
+		},
+	}
+
+	for _, tc := range testCases {
+		if got := IngestionTaskErrorCode(tc.err); got != tc.want {
+			t.Fatalf("%s: got %d, want %d", tc.name, got, tc.want)
+		}
+	}
+}