fix(theme): remove transition from body to fix VT snapshots

The CSS transition on the body's background-color (0.3s ease) was
causing the browser's View Transitions to capture a stale snapshot
during the Dark -> Light change. Even though the .dark class was
removed synchronously and we tried to disable transitions via an
!important override class, the interaction between Tailwind classes
and the raw CSS transition on body still caused the root VT snapshot
to render as Dark when it should have been Light.

By removing the transition from body entirely (which is redundant
anyway since we're using View Transitions for theme changes), the
body jumps to its target color instantly, guaranteeing the NEW
snapshot accurately reflects the final Light theme, eliminating
the 'ghost circle' or 'circle outline' bug.

input.css

@@ -36,7 +36,6 @@
     background-color: var(--color-paper-theme);
     color: var(--color-paper-primary);
     font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
-    transition: background-color 0.3s ease, color 0.3s ease;
     -webkit-font-smoothing: antialiased;
     -moz-osx-font-smoothing: grayscale;
   }