Migrate from .NET MAUI to Expo + Convex

Complete rewrite of Scry using TypeScript stack:

- Expo/React Native with Expo Router (file-based routing)
- Convex backend (serverless functions + real-time database)
- Adaptive camera system (expo-camera in Expo Go, Vision Camera in production)
- React Native Skia + fast-opencv for image processing
- GDPR-compliant auth setup with Zitadel OIDC (pending configuration)

Key features:
- Card recognition pipeline ported to TypeScript
- Perceptual hashing (192-bit color pHash)
- CLAHE preprocessing for lighting normalization
- Local SQLite cache with Convex sync
- Collection management with offline support

Removes all .NET/MAUI code (src/, test/, tools/).

💘 Generated with Crush

Assisted-by: Claude Opus 4.5 via Crush <crush@charm.land>

app/_layout.tsx

@@ -0,0 +1,72 @@
+import React, { useEffect } from "react";
+import FontAwesome from "@expo/vector-icons/FontAwesome";
+import { useFonts } from "expo-font";
+import * as SplashScreen from "expo-splash-screen";
+import { Stack } from "expo-router";
+import { ConvexProvider, ConvexReactClient } from "convex/react";
+import { HashCacheProvider } from "@/lib/context";
+import { useColorScheme } from "@/components/useColorScheme";
+
+// Initialize Convex client
+const convex = new ConvexReactClient(
+  process.env.EXPO_PUBLIC_CONVEX_URL as string
+);
+
+// Keep splash screen visible while loading fonts
+SplashScreen.preventAutoHideAsync();
+
+export default function RootLayout() {
+  const [loaded, error] = useFonts({
+    SpaceMono: require("../assets/fonts/SpaceMono-Regular.ttf"),
+    ...FontAwesome.font,
+  });
+
+  useEffect(() => {
+    if (error) throw error;
+  }, [error]);
+
+  useEffect(() => {
+    if (loaded) {
+      SplashScreen.hideAsync();
+    }
+  }, [loaded]);
+
+  if (!loaded) {
+    return null;
+  }
+
+  return (
+    <ConvexProvider client={convex}>
+      <HashCacheProvider>
+        <RootLayoutNav />
+      </HashCacheProvider>
+    </ConvexProvider>
+  );
+}
+
+function RootLayoutNav() {
+  const colorScheme = useColorScheme();
+
+  return (
+    <Stack
+      screenOptions={{
+        headerStyle: {
+          backgroundColor: colorScheme === "dark" ? "#1a1a1a" : "#fff",
+        },
+        headerTintColor: colorScheme === "dark" ? "#fff" : "#000",
+        contentStyle: {
+          backgroundColor: colorScheme === "dark" ? "#1a1a1a" : "#fff",
+        },
+      }}
+    >
+      <Stack.Screen name="(tabs)" options={{ headerShown: false }} />
+      <Stack.Screen
+        name="modal"
+        options={{
+          presentation: "modal",
+          title: "Card Details",
+        }}
+      />
+    </Stack>
+  );
+}