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/useClientOnlyValue.web.ts

@@ -0,0 +1,12 @@
+import React from 'react';
+
+// `useEffect` is not invoked during server rendering, meaning
+// we can use this to determine if we're on the server or not.
+export function useClientOnlyValue<S, C>(server: S, client: C): S | C {
+  const [value, setValue] = React.useState<S | C>(server);
+  React.useEffect(() => {
+    setValue(client);
+  }, [client]);
+
+  return value;
+}