chore: fix violations from the newly-enabled unicorn rules

Apply the code changes required by the rules enabled in the previous
commit: String() coercions over template literals, location.assign over
href assignment, URL#href over toString, Object.entries/values loop
forms, and related autofixes. Disable unicorn/no-non-function-verb-prefix,
and disable unicorn/no-error-property-assignment for test files.

Assisted-by: claude-code:opus-4.8

web_src/js/markup/render-iframe.ts

@@ -4,7 +4,7 @@ import {isDarkTheme} from '../utils.ts';
 
 function safeRenderIframeLink(link: any): string | null {
   try {
-    const url = new URL(`${link}`, window.location.href);
+    const url = new URL(link, window.location.href);
     if (url.protocol !== 'http:' && url.protocol !== 'https:') {
       console.error(`Unsupported link protocol: ${link}`);
       return null;