feat(app): add lightweight status access tracking

internal/auth/access_tracker.go

@@ -0,0 +1,81 @@
+package auth
+
+import (
+	"sort"
+	"sync"
+	"time"
+)
+
+type AccessSnapshot struct {
+	KeyID          string
+	LastPath       string
+	RemoteAddr     string
+	UserAgent      string
+	RequestCount   int
+	LastAccessedAt time.Time
+}
+
+type AccessTracker struct {
+	mu      sync.RWMutex
+	entries map[string]AccessSnapshot
+}
+
+func NewAccessTracker() *AccessTracker {
+	return &AccessTracker{entries: make(map[string]AccessSnapshot)}
+}
+
+func (t *AccessTracker) Record(keyID, path, remoteAddr, userAgent string, now time.Time) {
+	if t == nil || keyID == "" {
+		return
+	}
+
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	entry := t.entries[keyID]
+	entry.KeyID = keyID
+	entry.LastPath = path
+	entry.RemoteAddr = remoteAddr
+	entry.UserAgent = userAgent
+	entry.LastAccessedAt = now.UTC()
+	entry.RequestCount++
+	t.entries[keyID] = entry
+}
+
+func (t *AccessTracker) Snapshot() []AccessSnapshot {
+	if t == nil {
+		return nil
+	}
+
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+
+	items := make([]AccessSnapshot, 0, len(t.entries))
+	for _, entry := range t.entries {
+		items = append(items, entry)
+	}
+
+	sort.Slice(items, func(i, j int) bool {
+		return items[i].LastAccessedAt.After(items[j].LastAccessedAt)
+	})
+
+	return items
+}
+
+func (t *AccessTracker) ConnectedCount(now time.Time, window time.Duration) int {
+	if t == nil {
+		return 0
+	}
+
+	cutoff := now.UTC().Add(-window)
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+
+	count := 0
+	for _, entry := range t.entries {
+		if !entry.LastAccessedAt.Before(cutoff) {
+			count++
+		}
+	}
+	return count
+}