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>

components/ExternalLink.tsx

@@ -0,0 +1,25 @@
+import { Link } from 'expo-router';
+import * as WebBrowser from 'expo-web-browser';
+import React from 'react';
+import { Platform } from 'react-native';
+
+export function ExternalLink(
+  props: Omit<React.ComponentProps<typeof Link>, 'href'> & { href: string }
+) {
+  return (
+    <Link
+      target="_blank"
+      {...props}
+      // @ts-expect-error: External URLs are not typed.
+      href={props.href}
+      onPress={(e) => {
+        if (Platform.OS !== 'web') {
+          // Prevent the default behavior of linking to the default browser on native.
+          e.preventDefault();
+          // Open the link in an in-app browser.
+          WebBrowser.openBrowserAsync(props.href as string);
+        }
+      }}
+    />
+  );
+}