feat: add per-workout-type pace range and expected HR zone

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

backend/internal/store/workoutpaces.go

@@ -0,0 +1,69 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+)
+
+// WorkoutTypePace is a workout kind's user-declared target pace range and
+// expected HR zone. Informational only -- never read by the classification
+// rule engine. No history: fields are overwritten in place.
+type WorkoutTypePace struct {
+	WorkoutKindID   int64
+	PaceMinSecPerKm *float64
+	PaceMaxSecPerKm *float64
+	ExpectedHRZone  *int
+}
+
+func scanWorkoutTypePace(row interface{ Scan(...any) error }) (WorkoutTypePace, error) {
+	var p WorkoutTypePace
+	err := row.Scan(&p.WorkoutKindID, &p.PaceMinSecPerKm, &p.PaceMaxSecPerKm, &p.ExpectedHRZone)
+	return p, err
+}
+
+const workoutTypePaceColumns = `workout_kind_id, pace_min_sec_per_km, pace_max_sec_per_km, expected_hr_zone`
+
+// GetWorkoutTypePace fetches the pace/zone row for one workout kind.
+func (db *DB) GetWorkoutTypePace(ctx context.Context, workoutKindID int64) (WorkoutTypePace, error) {
+	row := db.QueryRowContext(ctx, `SELECT `+workoutTypePaceColumns+` FROM workout_type_paces WHERE workout_kind_id = ?`, workoutKindID)
+	p, err := scanWorkoutTypePace(row)
+	if err == sql.ErrNoRows {
+		return WorkoutTypePace{WorkoutKindID: workoutKindID}, nil
+	}
+	if err != nil {
+		return WorkoutTypePace{}, fmt.Errorf("get workout type pace for kind %d: %w", workoutKindID, err)
+	}
+	return p, nil
+}
+
+// UpdateWorkoutTypePace overwrites the pace/zone row for one workout kind.
+func (db *DB) UpdateWorkoutTypePace(ctx context.Context, p WorkoutTypePace) error {
+	_, err := db.ExecContext(ctx, `
+		UPDATE workout_type_paces SET pace_min_sec_per_km=?, pace_max_sec_per_km=?, expected_hr_zone=?
+		WHERE workout_kind_id=?`,
+		p.PaceMinSecPerKm, p.PaceMaxSecPerKm, p.ExpectedHRZone, p.WorkoutKindID)
+	if err != nil {
+		return fmt.Errorf("update workout type pace for kind %d: %w", p.WorkoutKindID, err)
+	}
+	return nil
+}
+
+// ListWorkoutTypePaces returns every workout kind's pace/zone row.
+func (db *DB) ListWorkoutTypePaces(ctx context.Context) ([]WorkoutTypePace, error) {
+	rows, err := db.QueryContext(ctx, `SELECT `+workoutTypePaceColumns+` FROM workout_type_paces ORDER BY workout_kind_id`)
+	if err != nil {
+		return nil, fmt.Errorf("list workout type paces: %w", err)
+	}
+	defer rows.Close()
+
+	paces := []WorkoutTypePace{}
+	for rows.Next() {
+		p, err := scanWorkoutTypePace(rows)
+		if err != nil {
+			return nil, fmt.Errorf("scan workout type pace row: %w", err)
+		}
+		paces = append(paces, p)
+	}
+	return paces, rows.Err()
+}