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, 4 insertions, 6 deletions

diff --git a/src/client/main.tsx b/src/client/main.tsx
index 4809bc1..a1d296a 100644
--- a/src/client/main.tsx
+++ b/src/client/main.tsx
@@ -1,7 +1,7 @@
 import { StrictMode } from "react";
 import { createRoot } from "react-dom/client";
 import { App } from "./App";
-import { AuthProvider, SyncProvider } from "./stores";
+import { StoreInitializer } from "./components/StoreInitializer";
 import "./styles.css";
 
 const rootElement = document.getElementById("root");
@@ -11,10 +11,8 @@ if (!rootElement) {
 
 createRoot(rootElement).render(
 	<StrictMode>
-		<AuthProvider>
-			<SyncProvider>
-				<App />
-			</SyncProvider>
-		</AuthProvider>
+		<StoreInitializer>
+			<App />
+		</StoreInitializer>
 	</StrictMode>,
 );