refactor(log): replace stdlib log with the application JSON logger

Every log.Printf/Fatalf becomes a structured slog call through
internal/log: request handlers use the request-scoped logger
(applog.FromContext, carrying request_id), startup failures exit via a
fatal() helper that still emits JSON, and the seedsample/dumpschema CLIs
bootstrap the same JSON logger. Stale client_test expectations aligned
with the refactored wrapper-call logging (message casing, result attr,
ERROR level).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/internal/store/profiles_test.go

@@ -0,0 +1,143 @@
+package store
+
+import (
+	"context"
+	"testing"
+)
+
+func TestProfile_DefaultsThenUpdate(t *testing.T) {
+	db := openTestDB(t)
+	ctx := context.Background()
+	userID, err := db.ProvisionUser(ctx, "test-sub", "Default")
+	if err != nil {
+		t.Fatalf("ProvisionUser: %v", err)
+	}
+
+	p, err := db.GetProfile(ctx, userID)
+	if err != nil {
+		t.Fatalf("GetProfile: %v", err)
+	}
+	if p.RollingWindowDays != 90 {
+		t.Errorf("RollingWindowDays = %d, want 90 (migration default)", p.RollingWindowDays)
+	}
+	if p.HRZone1MinPct != 50 || p.HRZone5MaxPct != 100 {
+		t.Errorf("zone defaults = %+v, want Z1 min=50, Z5 max=100", p)
+	}
+	if p.WarmupMinutes != 10 || p.CooldownMinutes != 5 {
+		t.Errorf("phase-minute defaults = %+v, want warmup=10, cooldown=5", p)
+	}
+	if p.BackfillHorizonDays != 90 {
+		t.Errorf("BackfillHorizonDays = %d, want 90 (schema default)", p.BackfillHorizonDays)
+	}
+	if p.MinRepresentativePaceSecPerKm != 720 || p.MinRepresentativeTimeSeconds != 3 {
+		t.Errorf("pace artifact filter defaults = %+v, want pace=720, time=3", p)
+	}
+	if p.PaceColor != "#3b82f6" || p.HeartRateColor != "#ef4444" {
+		t.Errorf("main line color defaults = %+v, want pace=#3b82f6, heartRate=#ef4444", p)
+	}
+	if p.WarmupColor != "#c2410c" || p.EffortColor != "#7c3aed" || p.RecoveryColor != "#15803d" || p.CooldownColor != "#fb923c" {
+		t.Errorf("effort color defaults = %+v", p)
+	}
+	if p.MainLineTintPct != 20 {
+		t.Errorf("MainLineTintPct = %v, want 20 (migration default)", p.MainLineTintPct)
+	}
+	if p.BackgroundDarkenPct != 35 {
+		t.Errorf("BackgroundDarkenPct = %v, want 35 (migration default)", p.BackgroundDarkenPct)
+	}
+	if p.TargetBrightenPct != 20 {
+		t.Errorf("TargetBrightenPct = %v, want 20 (migration default)", p.TargetBrightenPct)
+	}
+
+	maxHR, restingHR := 190.0, 50.0
+	p.PaceColor = "#111111"
+	p.EffortColor = "#222222"
+	p.MainLineTintPct = 45
+	p.BackgroundDarkenPct = 60
+	p.TargetBrightenPct = 50
+	p.GarminEmail = "runner@example.com"
+	p.GarminPassword = "hunter2"
+	p.RollingWindowDays = 120
+	p.MaxHeartRate = &maxHR
+	p.RestingHeartRate = &restingHR
+	p.WarmupMinutes = 8
+	p.BackfillHorizonDays = 14
+	p.MinRepresentativePaceSecPerKm = 600
+	p.MinRepresentativeTimeSeconds = 5
+
+	if err := db.UpdateProfile(ctx, userID, p); err != nil {
+		t.Fatalf("UpdateProfile: %v", err)
+	}
+
+	got, err := db.GetProfile(ctx, userID)
+	if err != nil {
+		t.Fatalf("GetProfile after update: %v", err)
+	}
+	if got.GarminEmail != "runner@example.com" || got.RollingWindowDays != 120 {
+		t.Errorf("got = %+v, want updated email/window", got)
+	}
+	if got.MaxHeartRate == nil || *got.MaxHeartRate != 190 {
+		t.Errorf("MaxHeartRate = %v, want 190", got.MaxHeartRate)
+	}
+	if got.WarmupMinutes != 8 {
+		t.Errorf("WarmupMinutes = %v, want 8", got.WarmupMinutes)
+	}
+	if got.BackfillHorizonDays != 14 {
+		t.Errorf("BackfillHorizonDays = %v, want 14", got.BackfillHorizonDays)
+	}
+	if got.MinRepresentativePaceSecPerKm != 600 || got.MinRepresentativeTimeSeconds != 5 {
+		t.Errorf("pace artifact filter after update = %+v, want pace=600, time=5", got)
+	}
+	if got.PaceColor != "#111111" || got.EffortColor != "#222222" {
+		t.Errorf("chart colors after update = %+v, want pace=#111111, effort=#222222", got)
+	}
+	if got.MainLineTintPct != 45 {
+		t.Errorf("MainLineTintPct after update = %v, want 45", got.MainLineTintPct)
+	}
+	if got.BackgroundDarkenPct != 60 {
+		t.Errorf("BackgroundDarkenPct after update = %v, want 60", got.BackgroundDarkenPct)
+	}
+	if got.TargetBrightenPct != 50 {
+		t.Errorf("TargetBrightenPct after update = %v, want 50", got.TargetBrightenPct)
+	}
+}
+
+func TestMarkGarminConnected_SetsTimestampOnceOnFirstCall(t *testing.T) {
+	db := openTestDB(t)
+	ctx := context.Background()
+	userID, err := db.ProvisionUser(ctx, "test-sub", "Test")
+	if err != nil {
+		t.Fatalf("ProvisionUser: %v", err)
+	}
+
+	before, err := db.GetProfile(ctx, userID)
+	if err != nil {
+		t.Fatalf("GetProfile: %v", err)
+	}
+	if before.GarminConnectedAt != nil {
+		t.Fatalf("expected a fresh profile to have nil GarminConnectedAt, got %v", *before.GarminConnectedAt)
+	}
+
+	if err := db.MarkGarminConnected(ctx, userID); err != nil {
+		t.Fatalf("MarkGarminConnected: %v", err)
+	}
+	afterFirst, err := db.GetProfile(ctx, userID)
+	if err != nil {
+		t.Fatalf("GetProfile after first mark: %v", err)
+	}
+	if afterFirst.GarminConnectedAt == nil {
+		t.Fatal("expected GarminConnectedAt to be set after MarkGarminConnected")
+	}
+	firstValue := *afterFirst.GarminConnectedAt
+
+	// A second call must not change the recorded first-connection time.
+	if err := db.MarkGarminConnected(ctx, userID); err != nil {
+		t.Fatalf("MarkGarminConnected (second call): %v", err)
+	}
+	afterSecond, err := db.GetProfile(ctx, userID)
+	if err != nil {
+		t.Fatalf("GetProfile after second mark: %v", err)
+	}
+	if afterSecond.GarminConnectedAt == nil || *afterSecond.GarminConnectedAt != firstValue {
+		t.Fatalf("GarminConnectedAt changed on second call: first=%q second=%v", firstValue, afterSecond.GarminConnectedAt)
+	}
+}