v3: code quality pass, various bug fixes

api/routes/preview.ts

@@ -3,6 +3,7 @@ import {
   fetchRichContent,
   isValidHttpUrl,
 } from "../services/rich-content-service.ts";
+import { APIErrorCode } from "../model/interfaces.ts";
 
 const previewRouter = new Router();
 
@@ -10,7 +11,10 @@ previewRouter.get("/api/preview", async (ctx) => {
   const url = ctx.request.url.searchParams.get("url") ?? "";
   if (!isValidHttpUrl(url)) {
     ctx.response.status = 400;
-    ctx.response.body = { success: false, error: { message: "Invalid URL" } };
+    ctx.response.body = {
+      success: false,
+      error: { code: APIErrorCode.VALIDATION_ERROR, message: "Invalid URL" },
+    };
     return;
   }
   const data = await fetchRichContent(url);