Add animated glass background, breadcrumbs, and brand mark polish

Cards now sit on an animated signature-gradient background and use a
translucent, blurred bp-glass surface so it shines through; extended
bp-glass to every stat surface on the Stats page and to its tab switcher.
Adds a Breadcrumbs component below the header on all app pages.

Also: drop the gradient text fill from the wordmark/heading, animate the
BrandMark's heart and curve on the dashboard hero instead of a plain pulse
ring, recenter the heart/curve artwork in icon.svg and BrandMark, close the
mobile nav menu on link click, remove the redundant "back to recordings"
button, and match the "Start session"/"Scan for devices" button sizes.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

components/control/RecordControls.tsx

@@ -28,7 +28,7 @@ export function RecordControls({ active, elapsedLabel, disabled, busy, onStart,
   }
 
   return (
-    <Button onClick={onStart} disabled={disabled || busy} size="sm">
+    <Button onClick={onStart} disabled={disabled || busy}>
       <Circle className="size-3.5" /> Start session
     </Button>
   );