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, 42 insertions, 0 deletions

diff --git a/src/client/atoms/index.ts b/src/client/atoms/index.ts
new file mode 100644
index 0000000..1e13222
--- /dev/null
+++ b/src/client/atoms/index.ts
@@ -0,0 +1,42 @@
+// Auth atoms
+export { SyncStatus } from "../sync";
+export {
+	authLoadingAtom,
+	isAuthenticatedAtom,
+	loginAtom,
+	logoutAtom,
+	useAuthInit,
+	userAtom,
+} from "./auth";
+
+// Cards atoms
+export { type Card, cardsByDeckAtomFamily } from "./cards";
+
+// Decks atoms
+export { type Deck, deckByIdAtomFamily, decksAtom } from "./decks";
+
+// NoteTypes atoms
+export { type NoteType, noteTypesAtom } from "./noteTypes";
+
+// Study atoms
+export {
+	type StudyCard,
+	type StudyData,
+	type StudyDeck,
+	studyDataAtomFamily,
+} from "./study";
+
+// Sync atoms
+export {
+	isOnlineAtom,
+	isSyncingAtom,
+	lastErrorAtom,
+	lastSyncAtAtom,
+	pendingCountAtom,
+	syncActionAtom,
+	syncStatusAtom,
+	useSyncInit,
+} from "./sync";
+
+// Utilities
+export { createReloadableAtom, createReloadableAtomFamily } from "./utils";