Use @gorhom/bottom-sheet for waypoint sheet

Replace custom View-based bottom sheet with @gorhom/bottom-sheet:
- Native gesture-driven drag, snap points, pan-down-to-close
- Proper safe area handling built in
- Wrap app with GestureHandlerRootView
- Add react-native-reanimated plugin to Expo config

Adds react-native-reanimated and react-native-gesture-handler as
native dependencies (requires new EAS build).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/mobile/app/_layout.tsx

@@ -1,5 +1,6 @@
 import { useEffect, useState } from "react";
 import { Stack, router } from "expo-router";
+import { GestureHandlerRootView } from "react-native-gesture-handler";
 import { Sentry, initSentry } from "../lib/sentry";
 import { isAuthenticated } from "../lib/auth";
 import { startVersionCheck } from "../lib/version-check";
@@ -22,7 +23,11 @@ function RootLayout() {
 
   if (!checked) return null;
 
-  return <Stack screenOptions={{ headerShown: false }} />;
+  return (
+    <GestureHandlerRootView style={{ flex: 1 }}>
+      <Stack screenOptions={{ headerShown: false }} />
+    </GestureHandlerRootView>
+  );
 }
 
 export default Sentry.wrap(RootLayout);