fitness: add per-exercise metrics, cardio support, and stats page

- Add metrics system (weight/reps/rpe/distance/duration) per exercise type
  so cardio exercises show distance+duration instead of weight+reps
- Add 8 new cardio exercises: swimming, hiking, rowing outdoor, cycling
  outdoor, elliptical, stair climber, jump rope, walking
- Add bilateral flag to dumbbell exercises for accurate tonnage calculation
- Make SetTable, SessionCard, history detail, template editor, and exercise
  stats API all render/compute dynamically based on exercise metrics
- Rename Profile to Stats with lifetime cards: workouts, tonnage, cardio km
- Move route /fitness/profile -> /fitness/stats, API /stats/profile -> /stats/overview

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

@@ -0,0 +1,161 @@
+import { json } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { requireAuth } from '$lib/server/middleware/auth';
+import { dbConnect } from '$utils/db';
+import { WorkoutSession } from '$models/WorkoutSession';
+import { BodyMeasurement } from '$models/BodyMeasurement';
+import { getExerciseById, getExerciseMetrics } from '$lib/data/exercises';
+
+export const GET: RequestHandler = async ({ locals }) => {
+	const user = await requireAuth(locals);
+	await dbConnect();
+
+	const tenWeeksAgo = new Date();
+	tenWeeksAgo.setDate(tenWeeksAgo.getDate() - 70);
+
+	const totalWorkouts = await WorkoutSession.countDocuments({ createdBy: user.nickname });
+
+	const weeklyAgg = await WorkoutSession.aggregate([
+		{
+			$match: {
+				createdBy: user.nickname,
+				startTime: { $gte: tenWeeksAgo }
+			}
+		},
+		{
+			$group: {
+				_id: {
+					year: { $isoWeekYear: '$startTime' },
+					week: { $isoWeek: '$startTime' }
+				},
+				count: { $sum: 1 }
+			}
+		},
+		{
+			$sort: { '_id.year': 1, '_id.week': 1 }
+		}
+	]);
+
+	// Lifetime totals: tonnage lifted + cardio km
+	const allSessions = await WorkoutSession.find(
+		{ createdBy: user.nickname },
+		{ 'exercises.exerciseId': 1, 'exercises.sets': 1 }
+	).lean();
+
+	let totalTonnage = 0;
+	let totalCardioKm = 0;
+	for (const s of allSessions) {
+		for (const ex of s.exercises) {
+			const exercise = getExerciseById(ex.exerciseId);
+			const metrics = getExerciseMetrics(exercise);
+			const isCardio = metrics.includes('distance');
+			const weightMultiplier = exercise?.bilateral ? 2 : 1;
+			for (const set of ex.sets) {
+				if (!set.completed) continue;
+				if (isCardio) {
+					totalCardioKm += set.distance ?? 0;
+				} else {
+					totalTonnage += (set.weight ?? 0) * weightMultiplier * (set.reps ?? 0);
+				}
+			}
+		}
+	}
+
+	const weightMeasurements = await BodyMeasurement.find(
+		{ createdBy: user.nickname, weight: { $ne: null } },
+		{ date: 1, weight: 1, _id: 0 }
+	)
+		.sort({ date: 1 })
+		.limit(30)
+		.lean();
+
+	// Build chart-ready workouts-per-week with filled gaps
+	const weekMap = new Map<string, number>();
+	for (const item of weeklyAgg) {
+		weekMap.set(`${item._id.year}-${item._id.week}`, item.count);
+	}
+
+	const allLabels: string[] = [];
+	const allData: number[] = [];
+	const now = new Date();
+	for (let i = 9; i >= 0; i--) {
+		const d = new Date(now);
+		d.setDate(d.getDate() - i * 7);
+		const year = getISOWeekYear(d);
+		const week = getISOWeek(d);
+		const key = `${year}-${week}`;
+		allLabels.push(`W${week}`);
+		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[];
+		data: number[];
+		sma: (number | null)[];
+		upper: (number | null)[];
+		lower: (number | null)[];
+	} = { labels: [], data: [], sma: [], upper: [], lower: [] };
+	const weights: number[] = [];
+	for (const m of weightMeasurements) {
+		const d = new Date(m.date);
+		weightChart.labels.push(
+			d.toLocaleDateString('en', { month: 'short', day: 'numeric' })
+		);
+		weightChart.data.push(m.weight!);
+		weights.push(m.weight!);
+	}
+
+	// Adaptive window: 7 if enough data, otherwise half the data (min 2)
+	const w = Math.min(7, Math.max(2, Math.floor(weights.length / 2)));
+	for (let i = 0; i < weights.length; i++) {
+		if (i < w - 1) {
+			weightChart.sma.push(null);
+			weightChart.upper.push(null);
+			weightChart.lower.push(null);
+		} else {
+			let sum = 0;
+			for (let j = i - w + 1; j <= i; j++) sum += weights[j];
+			const mean = sum / w;
+
+			let variance = 0;
+			for (let j = i - w + 1; j <= i; j++) variance += (weights[j] - mean) ** 2;
+			const std = Math.sqrt(variance / w);
+
+			const round = (v: number) => Math.round(v * 100) / 100;
+			weightChart.sma.push(round(mean));
+			weightChart.upper.push(round(mean + std));
+			weightChart.lower.push(round(mean - std));
+		}
+	}
+
+	return json({
+		totalWorkouts,
+		totalTonnage: Math.round(totalTonnage / 1000 * 10) / 10,
+		totalCardioKm: Math.round(totalCardioKm * 10) / 10,
+		workoutsChart,
+		weightChart
+	});
+};
+
+function getISOWeek(date: Date): number {
+	const d = new Date(date.getTime());
+	d.setHours(0, 0, 0, 0);
+	d.setDate(d.getDate() + 3 - ((d.getDay() + 6) % 7));
+	const week1 = new Date(d.getFullYear(), 0, 4);
+	return 1 + Math.round(((d.getTime() - week1.getTime()) / 86400000 - 3 + ((week1.getDay() + 6) % 7)) / 7);
+}
+
+function getISOWeekYear(date: Date): number {
+	const d = new Date(date.getTime());
+	d.setDate(d.getDate() + 3 - ((d.getDay() + 6) % 7));
+	return d.getFullYear();
+}