Remove everything that can change after first paint

Firefox users saw a flash on the first navigation after an idle spell, and
Chrome occasionally flashed white. Nothing in the network path explained it
(assets are immutable, the stylesheet is render-blocking, a cold Firefox
load paints fully styled), so this removes every remaining way a page could
look different between its first paint and its final state:

- Both Newsreader faces are embedded in the served stylesheet as data: URIs
  (CSP gains `font-src 'self' data:`; the preloads go away). A font fetched
  by URL is applied after first paint whenever the browser has to bring it
  back from disk, which is exactly the "first click after a while" case.
- The cross-document view transition is gone; the operator wants snappy.
- A color-scheme meta, kept in step with the saved theme, so the canvas the
  browser paints before the stylesheet is the right shade.
- The theme toggle's icon and label are chosen by CSS from html[data-theme]
  (set pre-paint by theme.js) instead of being rewritten by app.js.
- Dashboard table filters are rendered by the templates (shown under
  `.has-js`) rather than inserted by app.js, so tables no longer jump.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MD4VWGq6mGcd8Bg67qyx9k

src/web/templates/layout.html

@@ -3,25 +3,24 @@
 <head>
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
+  <meta name="color-scheme" content="light dark">
   <title>{{ page.title }} · The Daily EPUB</title>
   <script src="/static/theme.js?v={{ page.asset_version }}"></script>
-  <link rel="preload" href="/static/Newsreader.woff2" as="font" type="font/woff2" crossorigin>
-  <link rel="preload" href="/static/Newsreader-italic.woff2" as="font" type="font/woff2" crossorigin>
   <link rel="stylesheet" href="/static/app.css?v={{ page.asset_version }}">
   <link rel="alternate" type="application/atom+xml" title="The Daily EPUB" href="/feed.xml">
   <link rel="icon" href="/static/favicon.svg">
 </head>
 <body>
   <a class="fixed left-3 top-3 z-50 -translate-y-20 bg-ink px-3 py-2 font-sans text-sm text-paper no-underline focus:translate-y-0" href="#content">Skip to content</a>
-  <header class="site-header mx-auto max-w-7xl px-4 pt-4 sm:px-6 sm:pt-6">
+  <header class="mx-auto max-w-7xl px-4 pt-4 sm:px-6 sm:pt-6">
     <div class="mb-2 flex min-h-8 flex-nowrap items-center justify-between gap-2 border-b border-rule pb-2 font-sans text-[0.72rem] uppercase tracking-[0.12em] text-muted sm:gap-4">
       <div class="min-w-0 truncate whitespace-nowrap">{% block ears %}{% if page.is_dashboard() %}<span>Dashboard</span>{% endif %}{% endblock %}</div>
       <div class="flex shrink-0 items-center gap-2 whitespace-nowrap normal-case tracking-normal sm:gap-3">
         <button class="flex min-h-10 shrink-0 items-center gap-1.5 whitespace-nowrap border-0 bg-transparent px-1.5 py-1 text-xs text-muted hover:text-ink" type="button" data-theme-toggle aria-label="Theme: system">
           <svg data-theme-icon="system" aria-hidden="true" viewBox="0 0 24 24" class="h-4 w-4 fill-none stroke-current" stroke-width="1.75"><path d="M4 5.5h16v11H4zM9 20h6M12 16.5V20"/></svg>
-          <svg data-theme-icon="light" aria-hidden="true" viewBox="0 0 24 24" class="h-4 w-4 fill-none stroke-current" stroke-width="1.75" hidden><circle cx="12" cy="12" r="3.5"/><path d="M12 2v2.2M12 19.8V22M4.93 4.93l1.56 1.56M17.51 17.51l1.56 1.56M2 12h2.2M19.8 12H22M4.93 19.07l1.56-1.56M17.51 6.49l1.56-1.56"/></svg>
-          <svg data-theme-icon="dark" aria-hidden="true" viewBox="0 0 24 24" class="h-4 w-4 fill-none stroke-current" stroke-width="1.75" hidden><path d="M20 15.1A8.5 8.5 0 0 1 8.9 4a8.5 8.5 0 1 0 11.1 11.1Z"/></svg>
-          <span data-theme-label>System</span>
+          <svg data-theme-icon="light" aria-hidden="true" viewBox="0 0 24 24" class="h-4 w-4 fill-none stroke-current" stroke-width="1.75"><circle cx="12" cy="12" r="3.5"/><path d="M12 2v2.2M12 19.8V22M4.93 4.93l1.56 1.56M17.51 17.51l1.56 1.56M2 12h2.2M19.8 12H22M4.93 19.07l1.56-1.56M17.51 6.49l1.56-1.56"/></svg>
+          <svg data-theme-icon="dark" aria-hidden="true" viewBox="0 0 24 24" class="h-4 w-4 fill-none stroke-current" stroke-width="1.75"><path d="M20 15.1A8.5 8.5 0 0 1 8.9 4a8.5 8.5 0 1 0 11.1 11.1Z"/></svg>
+          <span data-theme-label="system">System</span><span data-theme-label="light">Light</span><span data-theme-label="dark">Dark</span>
         </button>
         {% match page.viewer %}{% when Some with (viewer) %}<a class="flex min-h-10 min-w-10 max-w-32 shrink-0 items-center justify-center truncate whitespace-nowrap px-1.5 text-ink no-underline hover:text-accent" href="/account">{{ viewer.username }}</a>{% when None %}<a class="flex min-h-10 min-w-10 shrink-0 items-center justify-center whitespace-nowrap px-1.5 text-ink no-underline hover:text-accent" href="/login">Sign in</a>{% endmatch %}
       </div>