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/camera/ExpoCamera.tsx

@@ -0,0 +1,48 @@
+/**
+ * Camera component using expo-camera (works in Expo Go).
+ */
+
+import React, { forwardRef, useImperativeHandle, useRef } from "react";
+import { StyleSheet } from "react-native";
+import { CameraView } from "expo-camera";
+
+export interface CameraHandle {
+  takePhoto: () => Promise<{ uri: string }>;
+}
+
+interface ExpoCameraProps {
+  flashEnabled?: boolean;
+}
+
+export const ExpoCamera = forwardRef<CameraHandle, ExpoCameraProps>(
+  ({ flashEnabled = false }, ref) => {
+    const cameraRef = useRef<CameraView>(null);
+
+    useImperativeHandle(ref, () => ({
+      takePhoto: async () => {
+        if (!cameraRef.current) {
+          throw new Error("Camera not ready");
+        }
+        const photo = await cameraRef.current.takePictureAsync({
+          quality: 0.8,
+          base64: false,
+        });
+        if (!photo) {
+          throw new Error("Failed to capture photo");
+        }
+        return { uri: photo.uri };
+      },
+    }));
+
+    return (
+      <CameraView
+        ref={cameraRef}
+        style={StyleSheet.absoluteFill}
+        facing="back"
+        flash={flashEnabled ? "on" : "off"}
+      />
+    );
+  }
+);
+
+ExpoCamera.displayName = "ExpoCamera";