Merge commit from fork

(cherry picked from commit d10fdfe9738b17a9d81037c031b40a2cc4cb8038)

* SP-2025-03.1 always wrap icon&thumbnail URLs

if they're not HTTP URLs, the frontend won't be able to display them
anyway (`<img src="mailto:…">` or '<div stile="background-image:
url(nntp:…)">` aren't going to work!), so let's always run them through the
media proxy, which will fail harder (fetching a `javascript:` URL
won't do anything in the backend, might do something in the frontend)
and will always protect the client's address in cases like `gemini:`
where the browser could try to fetch

* SP-2025-03.2 use object binding for more styles

interpolating a random (remote-controlled!) string into a `style`
attribute is a bad idea; using VueJS object binding, we should get
proper quoting and therefore safe parse failures instead of CSS
injections / XSS

* SP-2025-03.3 slightly more robust "self" URL handling

parse URLs instead of treating them as strings; this is still not
perfect, but the `URL` class only handles full URLs, not relative
ones, so there's so way to ask it "give me a URL object that
represents this resource relative to this base URL"

notice that passing very weird URLs to `MkUrl` and `MkUrlPreview` will
break the frontend (in dev mode) because there's an untrapped `new
URL(…)` that may explode; production builds seem to safely ignore the
error, though

---------

Co-authored-by: Julia <julia@insertdomain.name>
Co-authored-by: dakkar <dakkar@thenautilus.net>

packages/frontend/src/components/MkUserInfo.vue

@@ -5,7 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <template>
 <div class="_panel" :class="$style.root">
-	<div :class="$style.banner" :style="user.bannerUrl ? `background-image: url(${user.bannerUrl})` : ''"></div>
+	<div :class="$style.banner" :style="user.bannerUrl ? { backgroundImage: `url(${user.bannerUrl})` } : ''"></div>
 	<MkAvatar :class="$style.avatar" :user="user" indicator/>
 	<div :class="$style.title">
 		<MkA :class="$style.name" :to="userPage(user)"><MkUserName :user="user" :nowrap="false"/></MkA>