feat(auth): clear local IndexedDB and sync state on explicit logout

Wipe Dexie databases (main + CRDT sync state) and reset the sync queue
when the user explicitly logs out so the next account on the same device
starts from a clean local store. Session expiry deliberately keeps local
data intact so a returning user finds their offline work waiting.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/src/client/db/clear.ts b/src/client/db/clear.ts
new file mode 100644
index 0000000..589e5a5
--- /dev/null
+++ b/src/client/db/clear.ts
@@ -0,0 +1,25 @@
+import { crdtSyncStateManager } from "../sync/crdt/sync-state";
+import { syncQueue } from "../sync/queue";
+import { db } from "./index";
+
+/**
+ * Clears all locally persisted user-scoped data: the main IndexedDB tables,
+ * the sync queue state, and the CRDT sync state. Used at explicit logout to
+ * prevent the next user from seeing the previous user's offline data.
+ *
+ * Each step is isolated so that a partial failure (e.g. one tab still has the
+ * Dexie connection open) does not stop the rest from running.
+ */
+export async function clearAllLocalData(): Promise<void> {
+	const results = await Promise.allSettled([
+		syncQueue.reset(),
+		crdtSyncStateManager.clearAll(),
+		db.delete(),
+	]);
+
+	for (const result of results) {
+		if (result.status === "rejected") {
+			console.error("Failed to clear local data:", result.reason);
+		}
+	}
+}