Serve missing internal files as 404 instead of soft-404 page

## Issue
Requesting for an invalid js file like `https://odysee.com/public/some-non-existent-file.js` yields HTML, which is usually incorrectly redirect to an actual claim, or a soft-404 page.

It's not only showing incorrectly data, but it is being cached. This is one of the potential causes for the problem of users being stuck with bad cache.

## Approach
- In the final catch-all stage, try to detect if it's a file request, and return a 404 instead.
- Do no cache 404s. Same as https://community.cloudflare.com/t/404s-and-caching/337151. The file could eventually be corrected, but users remain stuck with 404.

## Concerns
- Is the detection too loose?

web/src/routes.js

@@ -70,6 +70,18 @@ router.get(`/$/rss/:claimName::claimId`, rssMiddleware);
 router.get(`/$/oembed`, oEmbedMiddleware);
 
 router.get('*', async (ctx) => {
+  const requestedUrl = ctx.url;
+
+  if (requestedUrl.startsWith('/public/') && requestedUrl.endsWith('.js')) {
+    // If the file exists, `app.use(serve(DIST_ROOT))` would have handled it.
+    // Handle the non-existent file here, otherwise it'll get resolved to a
+    // claim with the name 'public'.
+    ctx.status = 404;
+    ctx.body = 'Resource not found';
+    ctx.set('Cache-Control', 'no-store');
+    return;
+  }
+
   const html = await getHtml(ctx);
   ctx.body = html;
 });