Fix the logo's pop-in with a traced vector logo

The logo was an 880 KB SVG wrapping a 1254px PNG, downloaded again on
every page load. Keep that PNG as the master (artwork/logo.png) and have
scripts/logo.py trace it with potrace into a 6 KB logo.svg (favicon,
README) and logo.js, which brand.js draws inline in the header and on the
login page so the logo arrives with the page. Remove the unused
logo-white.svg.

Static files now carry content ETags, so reloads get 304s instead of
downloading the UI again.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/web/static/assets/brand.js

@@ -1,7 +1,12 @@
+// The Jarl logo and the login page's wordmark, drawn as inline SVG so they
+// appear together with the page instead of loading afterwards.
+//
 // The "JARL" wordmark for the login page: angular Norse-style letters
 // drawn as paths (no font needed), over a rule with DNS nodes. The letters
 // use the text color and the rule the accent color, so it follows the
 // theme.
+import * as logoData from "./logo.js";
+
 const NS = "http://www.w3.org/2000/svg";
 
 function el(tag, attrs, ...children) {
@@ -37,3 +42,11 @@ export function wordmark() {
   return el("svg", { class: "wordmark", viewBox: "-4 -4 288 162", role: "img", "aria-label": "Jarl" },
     el("title", null, "Jarl"), letterG, rule);
 }
+
+// logo returns the Jarl logo (traced from artwork/logo.png by
+// scripts/logo.py) as an SVG of the given size in pixels.
+export function logo(size, cls) {
+  return el("svg", { class: cls || "logo", width: size, height: size, viewBox: logoData.viewBox, "aria-hidden": "true", focusable: "false" },
+    el("g", { transform: logoData.transform },
+      ...logoData.layers.map(([fill, d]) => el("path", { fill, d }))));
+}