fix(app): improve light mode theming

- Make PaseoLogo theme-aware (uses foreground color instead of hardcoded white)
- Add shadow tokens (sm/md/lg) to theme with per-scheme opacity, radius, and offset
- Replace all 16 hardcoded shadow instances with spreadable theme.shadow tokens
- Fix button icon color for default variant (use accentForeground, not foreground)
- Fix dark background flash on startup (root layout used hardcoded darkTheme)
- Add theme.colorScheme to replace fragile hex-string dark mode detection
- Add scrollbarHandle and surfaceWorkspace tokens to eliminate isDark branching

packages/app/src/components/ui/tooltip.tsx

@@ -535,11 +535,7 @@ const styles = StyleSheet.create((theme) => ({
     backgroundColor: theme.colors.popover,
     borderWidth: theme.borderWidth[2],
     borderColor: theme.colors.border,
-    shadowColor: "#000",
-    shadowOpacity: 0.2,
-    shadowRadius: 12,
-    shadowOffset: { width: 0, height: 6 },
-    elevation: 6,
+    ...theme.shadow.sm,
     zIndex: 1000,
   },
 }));