fix(offline): harden sync catch + add queue/sync test coverage + atomic transactions

src/lib/offline/queue.ts

@@ -13,8 +13,15 @@ export async function enqueueAction(
 ): Promise<QueuedAction> {
   const db = await getOfflineDB();
   const id = options.id ?? uuidv4();
-  const existing = await db.get("queue", id);
-  if (existing) return existing;
+  // Atomic read-then-write inside a single readwrite transaction so two
+  // concurrent calls with the same explicit `id` can't both pass the
+  // existence check and write twice.
+  const tx = db.transaction("queue", "readwrite");
+  const existing = await tx.store.get(id);
+  if (existing) {
+    await tx.done;
+    return existing;
+  }
   const action: QueuedAction = {
     id,
     actionName,
@@ -24,7 +31,8 @@ export async function enqueueAction(
     lastAttemptAt: null,
     status: "pending",
   };
-  await db.put("queue", action);
+  await tx.store.put(action);
+  await tx.done;
   return action;
 }
 
@@ -49,12 +57,17 @@ export async function dequeueAction(id: string): Promise<QueuedAction | null> {
 
 export async function markInFlight(id: string): Promise<void> {
   const db = await getOfflineDB();
-  const action = await db.get("queue", id);
-  if (!action) return;
+  const tx = db.transaction("queue", "readwrite");
+  const action = await tx.store.get(id);
+  if (!action) {
+    await tx.done;
+    return;
+  }
   action.status = "in-flight";
   action.lastAttemptAt = Date.now();
   action.attempts += 1;
-  await db.put("queue", action);
+  await tx.store.put(action);
+  await tx.done;
 }
 
 export async function markSynced(id: string): Promise<void> {
@@ -64,20 +77,30 @@ export async function markSynced(id: string): Promise<void> {
 
 export async function markConflict(id: string, error: string): Promise<void> {
   const db = await getOfflineDB();
-  const action = await db.get("queue", id);
-  if (!action) return;
+  const tx = db.transaction("queue", "readwrite");
+  const action = await tx.store.get(id);
+  if (!action) {
+    await tx.done;
+    return;
+  }
   action.status = "conflict";
   action.error = error;
-  await db.put("queue", action);
+  await tx.store.put(action);
+  await tx.done;
 }
 
 export async function markFailed(id: string, error: string): Promise<void> {
   const db = await getOfflineDB();
-  const action = await db.get("queue", id);
-  if (!action) return;
+  const tx = db.transaction("queue", "readwrite");
+  const action = await tx.store.get(id);
+  if (!action) {
+    await tx.done;
+    return;
+  }
   action.status = "failed";
   action.error = error;
   action.attempts += 1;
   action.lastAttemptAt = Date.now();
-  await db.put("queue", action);
+  await tx.store.put(action);
+  await tx.done;
 }