fitness: limit workouts-per-week chart to 10 weeks and trim empty leading weeks

Reduce the chart window from 12 to 10 weeks and trim leading weeks
with zero workouts so the chart starts from the first week with data.

src/routes/api/fitness/stats/profile/+server.ts

@@ -16,8 +16,8 @@ export const GET: RequestHandler = async ({ locals }) => {
 	await dbConnect();
 	console.timeEnd('[stats/profile] dbConnect');
 
-	const twelveWeeksAgo = new Date();
+	const tenWeeksAgo = new Date();
-	twelveWeeksAgo.setDate(twelveWeeksAgo.getDate() - 84);
+	tenWeeksAgo.setDate(tenWeeksAgo.getDate() - 70);
 
 	console.time('[stats/profile] countDocuments');
 	const totalWorkouts = await WorkoutSession.countDocuments({ createdBy: user.nickname });
@@ -28,7 +28,7 @@ export const GET: RequestHandler = async ({ locals }) => {
 		{
 			$match: {
 				createdBy: user.nickname,
-				startTime: { $gte: twelveWeeksAgo }
+				startTime: { $gte: tenWeeksAgo }
 			}
 		},
 		{
@@ -62,18 +62,27 @@ export const GET: RequestHandler = async ({ locals }) => {
 		weekMap.set(`${item._id.year}-${item._id.week}`, item.count);
 	}
 
-	const workoutsChart: { labels: string[]; data: number[] } = { labels: [], data: [] };
+	const allLabels: string[] = [];
+	const allData: number[] = [];
 	const now = new Date();
-	for (let i = 11; i >= 0; i--) {
+	for (let i = 9; i >= 0; i--) {
 		const d = new Date(now);
 		d.setDate(d.getDate() - i * 7);
 		const year = getISOWeekYear(d);
 		const week = getISOWeek(d);
 		const key = `${year}-${week}`;
-		workoutsChart.labels.push(`W${week}`);
+		allLabels.push(`W${week}`);
-		workoutsChart.data.push(weekMap.get(key) ?? 0);
+		allData.push(weekMap.get(key) ?? 0);
 	}
 
+	// Trim leading empty weeks, but always keep from first week with data
+	let firstNonZero = allData.findIndex((v) => v > 0);
+	if (firstNonZero === -1) firstNonZero = allData.length - 1; // show at least current week
+	const workoutsChart = {
+		labels: allLabels.slice(firstNonZero),
+		data: allData.slice(firstNonZero)
+	};
+
 	// Build chart-ready weight data with SMA ± 1 std dev confidence band
 	const weightChart: {
 		labels: string[];