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/Themed.tsx

@@ -0,0 +1,45 @@
+/**
+ * Learn more about Light and Dark modes:
+ * https://docs.expo.io/guides/color-schemes/
+ */
+
+import { Text as DefaultText, View as DefaultView } from 'react-native';
+
+import Colors from '@/constants/Colors';
+import { useColorScheme } from './useColorScheme';
+
+type ThemeProps = {
+  lightColor?: string;
+  darkColor?: string;
+};
+
+export type TextProps = ThemeProps & DefaultText['props'];
+export type ViewProps = ThemeProps & DefaultView['props'];
+
+export function useThemeColor(
+  props: { light?: string; dark?: string },
+  colorName: keyof typeof Colors.light & keyof typeof Colors.dark
+) {
+  const theme = useColorScheme() ?? 'light';
+  const colorFromProps = props[theme];
+
+  if (colorFromProps) {
+    return colorFromProps;
+  } else {
+    return Colors[theme][colorName];
+  }
+}
+
+export function Text(props: TextProps) {
+  const { style, lightColor, darkColor, ...otherProps } = props;
+  const color = useThemeColor({ light: lightColor, dark: darkColor }, 'text');
+
+  return <DefaultText style={[{ color }, style]} {...otherProps} />;
+}
+
+export function View(props: ViewProps) {
+  const { style, lightColor, darkColor, ...otherProps } = props;
+  const backgroundColor = useThemeColor({ light: lightColor, dark: darkColor }, 'background');
+
+  return <DefaultView style={[{ backgroundColor }, style]} {...otherProps} />;
+}