Fix insecure images

On the homepage, there are links served from insecure domains. This makes the padlock in Firefox's URL bar gray with a caution sign.

Here's a function I made for .tech:

```js
function makeImageSourceSecure(url) {
const originalUrl = new URL(url);

if (originalUrl.protocol !== "https")
return `https://${originalUrl.host}${originalUrl.pathname}`;

return originalUrl.href;
}
```

Locate the homepage code that constructs or renders image URLs, then inspect how insecure-domain links are produced. Use the supplied makeImageSourceSecure behavior as a reference and verify that homepage images no longer trigger Firefox's mixed-content warning.

Written by the indexing model from the issue text.