refactor(client): migrate state management from React Context to Jotai

Replace AuthProvider and SyncProvider with Jotai atoms for more granular
state management and better performance. This migration:

- Creates atoms for auth, sync, decks, cards, noteTypes, and study state
- Uses atomFamily for parameterized state (e.g., cards by deckId)
- Introduces StoreInitializer component for subscription initialization
- Updates all components and pages to use useAtomValue/useSetAtom
- Updates all tests to use Jotai Provider with createStore pattern

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

1 files changed, 0 insertions, 15 deletions

diff --git a/src/client/stores/index.ts b/src/client/stores/index.ts
deleted file mode 100644
index c7f6241..0000000
--- a/src/client/stores/index.ts
+++ /dev/null
@@ -1,15 +0,0 @@
-export type {
-	AuthActions,
-	AuthContextValue,
-	AuthProviderProps,
-	AuthState,
-} from "./auth";
-export { ApiClientError, AuthProvider, useAuth } from "./auth";
-
-export type {
-	SyncActions,
-	SyncContextValue,
-	SyncProviderProps,
-	SyncState,
-} from "./sync";
-export { SyncProvider, useSync } from "./sync";