Add WCAG 2.1 Level AA accessibility across all components

src/App.svelte

@@ -52,10 +52,28 @@
     };
   });
 
-  // Transition parameters
-  const DURATION = 700;
+  // Reduced motion preference
+  let reducedMotion = $state(window.matchMedia("(prefers-reduced-motion: reduce)").matches);
+  $effect(() => {
+    const mq = window.matchMedia("(prefers-reduced-motion: reduce)");
+    const handler = (e: MediaQueryListEvent) => { reducedMotion = e.matches; };
+    mq.addEventListener("change", handler);
+    return () => mq.removeEventListener("change", handler);
+  });
+
+  // Transition parameters - zero when reduced motion active
+  const DURATION = $derived(reducedMotion ? 0 : 700);
   const easing = cubicOut;
 
+  // Focus management: move focus to new view's heading on view change
+  $effect(() => {
+    const _view = effectiveView;
+    requestAnimationFrame(() => {
+      const heading = document.querySelector("h1[tabindex='-1']") as HTMLElement | null;
+      heading?.focus({ preventScroll: true });
+    });
+  });
+
   // When fullscreen_mode is OFF, the separate break window handles breaks,
   // so the main window should keep showing whatever view it was on (dashboard).
   const effectiveView = $derived(
@@ -65,7 +83,7 @@
   );
 </script>
 
-<div class="relative h-full bg-black">
+<main class="relative h-full bg-black">
   {#if $config.background_blobs_enabled}
     <BackgroundBlobs accentColor={$config.accent_color} breakColor={$config.break_color} />
   {/if}
@@ -115,4 +133,4 @@
       </div>
     {/if}
   </div>
-</div>
+</main>