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>

lib/hooks/useConvex.ts

@@ -0,0 +1,101 @@
+/**
+ * Hooks for Convex data access.
+ */
+
+import { useQuery, useMutation } from "convex/react";
+import { api } from "../../convex/_generated/api";
+import { useHashCache } from "../context";
+import { useEffect } from "react";
+import type { CardHashEntry } from "../recognition";
+import type { Id } from "../../convex/_generated/dataModel";
+
+type User = { _id: Id<"users"> } | null | undefined;
+
+/**
+ * Hook to get the current authenticated user.
+ * Returns unauthenticated state when auth is not configured.
+ */
+export function useCurrentUser(): { user: User; isLoading: boolean; isAuthenticated: boolean } {
+  // When using ConvexProvider (no auth), just return unauthenticated state
+  // Switch to ConvexAuthProvider + useConvexAuth when Zitadel is configured
+  return {
+    user: null,
+    isLoading: false,
+    isAuthenticated: false,
+  };
+}
+
+/**
+ * Hook to fetch and cache card hashes from Convex.
+ */
+export function useCardHashes() {
+  const { setCardHashes, hashesLoaded, lastHashSync, cardHashes } = useHashCache();
+  
+  // Fetch all cards from Convex
+  const cards = useQuery(api.cards.list);
+  
+  useEffect(() => {
+    if (cards) {
+      // Convert Convex cards to CardHashEntry format
+      const entries: CardHashEntry[] = cards.map((card) => ({
+        id: card.scryfallId,
+        name: card.name,
+        setCode: card.setCode,
+        collectorNumber: card.collectorNumber,
+        imageUri: card.imageUri,
+        hash: new Uint8Array(card.hash),
+      }));
+      
+      setCardHashes(entries);
+    }
+  }, [cards, setCardHashes]);
+  
+  return {
+    loading: cards === undefined && !hashesLoaded,
+    loaded: hashesLoaded,
+    count: cardHashes.length,
+    lastSync: lastHashSync,
+    hashes: cardHashes,
+  };
+}
+
+/**
+ * Hook to get card count.
+ */
+export function useCardCount() {
+  const count = useQuery(api.cards.count);
+  return count ?? 0;
+}
+
+/**
+ * Hook to search cards by name.
+ */
+export function useSearchCards(query: string) {
+  const results = useQuery(
+    api.cards.searchByName,
+    query.length >= 2 ? { name: query } : "skip"
+  );
+  return results ?? [];
+}
+
+/**
+ * Hook to manage collection.
+ */
+export function useCollection(userId?: string) {
+  const collection = useQuery(
+    api.collections.getByUser,
+    userId ? { userId: userId as any } : "skip"
+  );
+  
+  const addCard = useMutation(api.collections.add);
+  const removeCard = useMutation(api.collections.remove);
+  const updateQuantity = useMutation(api.collections.updateQuantity);
+  
+  return {
+    collection: collection ?? [],
+    addCard,
+    removeCard,
+    updateQuantity,
+    loading: collection === undefined,
+  };
+}