fix: sync rest timer exercise/set indices across sessions

restExerciseIdx and restSetIdx were sent by the client but never
persisted server-side, so other sessions couldn't display which
exercise/set the rest timer belonged to.

src/models/ActiveWorkout.ts

@@ -25,6 +25,8 @@ export interface IActiveWorkout {
   savedAt: number;
   restStartedAt: number | null;
   restTotal: number;
+  restExerciseIdx: number;
+  restSetIdx: number;
   updatedAt?: Date;
 }
 
@@ -87,6 +89,14 @@ const ActiveWorkoutSchema = new mongoose.Schema(
     restTotal: {
       type: Number,
       default: 0
+    },
+    restExerciseIdx: {
+      type: Number,
+      default: -1
+    },
+    restSetIdx: {
+      type: Number,
+      default: -1
     }
   },
   {

src/routes/api/fitness/workout/active/+server.ts

@@ -34,7 +34,7 @@ export const PUT: RequestHandler = async ({ request, locals }) => {
   try {
     await dbConnect();
     const data = await request.json();
-    const { name, templateId, exercises, paused, elapsed, savedAt, expectedVersion, restStartedAt, restTotal } = data;
+    const { name, templateId, exercises, paused, elapsed, savedAt, expectedVersion, restStartedAt, restTotal, restExerciseIdx, restSetIdx } = data;
 
     if (!name) {
       return json({ error: 'Name is required' }, { status: 400 });
@@ -65,6 +65,8 @@ export const PUT: RequestHandler = async ({ request, locals }) => {
           savedAt: savedAt ?? Date.now(),
           restStartedAt: restStartedAt ?? null,
           restTotal: restTotal ?? 0,
+          restExerciseIdx: restExerciseIdx ?? -1,
+          restSetIdx: restSetIdx ?? -1,
           version: newVersion
         },
         $setOnInsert: { userId }