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>

convex/auth.ts

@@ -0,0 +1,48 @@
+/**
+ * Convex Auth configuration with Zitadel OIDC.
+ * 
+ * GDPR Compliance: No user profile data (name, email, image) is stored.
+ * User details must be fetched from Zitadel userinfo endpoint when needed.
+ */
+
+import Zitadel from "@auth/core/providers/zitadel";
+import { convexAuth } from "@convex-dev/auth/server";
+
+export const { auth, signIn, signOut, store, isAuthenticated } = convexAuth({
+  providers: [
+    Zitadel({
+      issuer: process.env.AUTH_ZITADEL_ISSUER,
+      clientId: process.env.AUTH_ZITADEL_ID,
+      clientSecret: process.env.AUTH_ZITADEL_SECRET,
+      // Strip all profile data - return only the subject ID
+      profile(zitadelProfile) {
+        return {
+          id: zitadelProfile.sub,
+          // Intentionally omit: name, email, image
+          // These must be fetched from Zitadel userinfo endpoint
+        };
+      },
+    }),
+  ],
+  callbacks: {
+    // Validate redirect URIs for React Native
+    async redirect({ redirectTo }) {
+      const allowedPrefixes = [
+        "scry://",     // App custom scheme
+        "app://",      // Default Expo scheme
+        "exp://",      // Expo Go
+        "http://localhost",
+        "https://localhost",
+      ];
+
+      const isAllowed = allowedPrefixes.some((prefix) =>
+        redirectTo.startsWith(prefix)
+      );
+
+      if (!isAllowed) {
+        throw new Error(`Invalid redirectTo URI: ${redirectTo}`);
+      }
+      return redirectTo;
+    },
+  },
+});