fix(app): soften the compact composer shadow in light mode (#7214)

The compact composer used a hardcoded box shadow shared by both themes,
so it read as a heavy band on light backgrounds. It now uses the shared
sm shadow token, whose light value is raised from 0.02 to 0.08 opacity
so the lift stays visible. Dark sm is unchanged.

packages/app/src/composer/input/input.tsx

@@ -2226,7 +2226,7 @@ const styles = StyleSheet.create((theme: Theme) => ({
   },
   // Lifts the composer off the chat it sits under on phones.
   inputWrapperCompact: {
-    boxShadow: "0px 4px 16px rgba(0, 0, 0, 0.2)",
+    ...theme.shadow.sm,
   },
   // Dotted says "this surface is the same box, but there is nothing to type
   // into it" without swapping the border colour, which reads as an error state.

packages/app/src/styles/theme.ts

@@ -741,7 +741,7 @@ export const darkPureBlackTheme = buildDarkTheme(pureBlackDarkColors);
 
 const lightShadow = {
   sm: {
-    shadowColor: "rgba(0, 0, 0, 0.02)",
+    shadowColor: "rgba(0, 0, 0, 0.08)",
     shadowOffset: { width: 0, height: 2 },
     shadowRadius: 8,
     elevation: 2,