Add Race workout kind with Garmin eventType auto-detection, sync-time running filter, and pill-based review queue filter

Race is the 8th fixed workout kind, seeded with a real (not placeholder)
rule since Garmin Connect's eventType.typeKey reports "race" for
manually-tagged race activities. Non-running activity types (padel,
cycling, strength training, ...) are now dropped at sync time instead of
being stored. The Review Queue's type filter is now clickable exclusive
pill buttons instead of a dropdown.

backend/internal/sync/mapping.go

@@ -2,6 +2,7 @@ package sync
 
 import (
 	"encoding/json"
+	"strings"
 	"time"
 
 	"smartrun/backend/internal/classify"
@@ -9,11 +10,21 @@ import (
 	"smartrun/backend/internal/store"
 )
 
+// isRunningActivityType reports whether a Garmin activityType.typeKey
+// represents a running activity (running, trail_running, treadmill_running,
+// track_running, indoor_running, virtual_run, ...) as opposed to other
+// sports (padel, cycling, strength training, ...) that also show up in
+// get_activities().
+func isRunningActivityType(typeKey string) bool {
+	return strings.Contains(strings.ToLower(typeKey), "run")
+}
+
 func toActivityRow(a garmin.Activity) store.Activity {
 	return store.Activity{
 		GarminActivityID:        a.ActivityID,
 		ActivityName:            a.ActivityName,
 		ActivityType:            a.ActivityType.TypeKey,
+		EventTypeKey:            a.EventType.TypeKey,
 		StartTimeUTC:            a.StartTimeGMT,
 		BeginTimestampMs:        a.BeginTimestamp,
 		DurationSeconds:         a.Duration,
@@ -125,9 +136,14 @@ func toSampleRows(samples []garmin.Sample) []store.Sample {
 // rules. maxHR is the user's configured max heart rate, used only to derive
 // avg_hr_pct_max (Garmin's activity/lap summaries don't include it directly).
 func buildMetricContext(a store.Activity, laps []store.Lap, maxHR float64) classify.MetricContext {
+	isRace := 0.0
+	if a.EventTypeKey == "race" {
+		isRace = 1.0
+	}
 	ctx := classify.MetricContext{
 		"duration_seconds": a.DurationSeconds,
 		"distance_meters":  a.DistanceMeters,
+		"is_race":          isRace,
 	}
 	if a.AvgSpeedMps != nil && *a.AvgSpeedMps > 0 {
 		ctx["avg_pace_sec_per_km"] = 1000 / *a.AvgSpeedMps