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/(tabs)/_layout.tsx

@@ -0,0 +1,58 @@
+import React from "react";
+import FontAwesome from "@expo/vector-icons/FontAwesome";
+import { Tabs } from "expo-router";
+import { useColorScheme } from "@/components/useColorScheme";
+import Colors from "@/constants/Colors";
+
+function TabBarIcon(props: {
+  name: React.ComponentProps<typeof FontAwesome>["name"];
+  color: string;
+}) {
+  return <FontAwesome size={24} style={{ marginBottom: -3 }} {...props} />;
+}
+
+export default function TabLayout() {
+  const colorScheme = useColorScheme();
+
+  return (
+    <Tabs
+      screenOptions={{
+        tabBarActiveTintColor: Colors[colorScheme ?? "light"].tint,
+        tabBarInactiveTintColor: "#888",
+        tabBarStyle: {
+          backgroundColor: colorScheme === "dark" ? "#1a1a1a" : "#fff",
+          borderTopColor: colorScheme === "dark" ? "#333" : "#eee",
+        },
+        headerStyle: {
+          backgroundColor: colorScheme === "dark" ? "#1a1a1a" : "#fff",
+        },
+        headerTintColor: colorScheme === "dark" ? "#fff" : "#000",
+      }}
+    >
+      <Tabs.Screen
+        name="index"
+        options={{
+          title: "Collection",
+          tabBarIcon: ({ color }) => (
+            <TabBarIcon name="th-large" color={color} />
+          ),
+        }}
+      />
+      <Tabs.Screen
+        name="scan"
+        options={{
+          title: "Scan",
+          headerShown: false,
+          tabBarIcon: ({ color }) => <TabBarIcon name="camera" color={color} />,
+        }}
+      />
+      <Tabs.Screen
+        name="settings"
+        options={{
+          title: "Settings",
+          tabBarIcon: ({ color }) => <TabBarIcon name="cog" color={color} />,
+        }}
+      />
+    </Tabs>
+  );
+}