fix: handle correct type conversion for relation fields

Updated `RelationField` to dynamically determine the type based on `target_field_type`. Added a test for proper TypeScript generation with text primary fields in system entities.

app/src/data/entities/EntityTypescript.spec.ts

@@ -21,4 +21,34 @@ describe("EntityTypescript", () => {
       const et = new EntityTypescript(schema.proto.withConnection(new DummyConnection()));
       expect(et.toString()).toContain('users?: DB["users"];');
    });
+
+   it("should generate correct typescript for system entities with uuid primary field", () => {
+      const schema = proto.em(
+         {
+            test: proto.entity(
+               "test",
+               {
+                  name: proto.text(),
+               },
+               {
+                  primary_format: "uuid",
+               },
+            ),
+            users: proto.systemEntity(
+               "users",
+               {
+                  name: proto.text(),
+               },
+               {
+                  primary_format: "uuid",
+               },
+            ),
+         },
+         ({ relation }, { test, users }) => {
+            relation(test).manyToOne(users);
+         },
+      );
+      const et = new EntityTypescript(schema.proto.withConnection(new DummyConnection()));
+      expect(et.toString()).toContain("users_id?: string;");
+   });
 });

app/src/data/relations/RelationField.ts

@@ -84,9 +84,10 @@ export class RelationField extends Field<RelationFieldConfig> {
    }
 
    override toType(): TFieldTSType {
+      const type = this.config.target_field_type === "integer" ? "number" : "string";
       return {
          ...super.toType(),
-         type: "number",
+         type,
       };
    }
 }