Flatten Astronaut

This reduces the size of the astronaut asset (~10x) and thereby the
canister size (by ~25%).

A single frame of the original animated astronaut is extracted, and a
simple "floating" CSS animation is used to make the astronaut look
lively.

src/frontend/src/components/loader.ts

@@ -1,5 +1,5 @@
 import { html, render } from "lit-html";
-import loaderUrl from "./loader.webp";
+import loaderUrl from "./loader.png";
 
 const loader = () => html` <div id="loader" class="c-loader">
   <img class="c-loader__image" src=${loaderUrl} alt="loading" />

src/frontend/src/spa.ts

@@ -1,4 +1,4 @@
-import loaderUrl from "$src/components/loader.webp";
+import loaderUrl from "$src/components/loader.png";
 import { showWarningIfNecessary } from "./banner";
 import { displayError } from "./components/displayError";
 import { anyFeatures, features } from "./features";

src/frontend/src/styles/main.css

@@ -2735,14 +2735,32 @@ input[type="checkbox"] {
   background: var(--rc-overlay-backdrop);
 }
 
+/* Pretend the astronaut is moving in space */
+@keyframes astrodance {
+  0% {
+    transform: translate(-50%, -50%) rotate(-20deg);
+  }
+
+  50% {
+    transform: translate(-50%, -50%) rotate(10deg);
+  }
+
+  100% {
+    transform: translate(-50%, -50%) rotate(-20deg);
+  }
+}
+
 .c-loader__image {
-  width: 125px;
+  width: 64px;
   display: block;
   position: absolute;
   top: 50%;
   left: 50%;
-  transform: translate(-50%, -50%);
   user-select: none;
+  animation-name: astrodance;
+  animation-duration: 5s;
+  animation-iteration-count: infinite;
+  animation-timing-function: ease-in-out;
 }
 
 /* Wrap QR codes in a white square (for legibility) and prettify a bit */