Modern in the logo's colours, and the logo in the page's mode (#63)

Modern's palette was sampled from the 2004 iPodderX icon: a neutral navy,
its screen blue and amber EQ bars. It now takes the new logo's colours,
the dark half from logo-dark.svg (navy ground, #8fc2ea scale, #ff6a1a
needle) and the light half from logo.svg (sky ground, #2f6aa0 scale, the
needle taken down to #c43e00 so white on it clears AA). The pending amber
and the error red moved apart from the needle's orange, and the sign-in
page's copy of the palette follows.

The pages always showed logo.svg, the light variant, even in a dark
theme; logo-dark.svg was never served. It is now, and the app and admin
pages show whichever matches data-mode, dark until the script says light,
as the palette is. The sign-in page, which has no account's theme, picks
by the system's with <picture>.

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

web/build.mjs

@@ -75,7 +75,7 @@ export function buildPage(name, { minify = true } = {}) {
   // The icons are named by their contents too. They are kept a day under a fixed name, and a new
   // logo went unseen for that day, in browsers and at Cloudflare's edge. The server ignores the
   // query; /favicon.ico, which a browser asks for on its own, cannot carry one.
-  out = out.replace(/(href|src)="\/(favicon\.png|apple-touch-icon\.png|logo\.svg)"/g,
+  out = out.replace(/(href|src|srcset)="\/(favicon\.png|apple-touch-icon\.png|logo\.svg|logo-dark\.svg)"/g,
     (_, attr, file) => `${attr}="/${file}?v=${hash(fs.readFileSync(path.join(here, file)))}"`);
   if (!minify) return { html: out, js, script };
   const r = html.minifySync(out, { minifyJs: false, minifyCss: true, removeComments: true });