feat: add session indicators and top exec commands to dashboard

Add visual indicators to session tables (replay badge when events exist,
exec badge for exec sessions) and a new "Top Exec Commands" table on the
dashboard. Includes EventCount field on Session, GetTopExecCommands on
Store interface, and truncateCommand template function.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/storage/store.go

@@ -28,6 +28,7 @@ type Session struct {
 	DisconnectedAt *time.Time
 	HumanScore     *float64
 	ExecCommand    *string
+	EventCount     int
 }
 
 // SessionLog represents a single log entry for a session.
@@ -102,6 +103,9 @@ type Store interface {
 	// GetTopCountries returns the top N countries by total attempt count.
 	GetTopCountries(ctx context.Context, limit int) ([]TopEntry, error)
 
+	// GetTopExecCommands returns the top N exec commands by session count.
+	GetTopExecCommands(ctx context.Context, limit int) ([]TopEntry, error)
+
 	// GetRecentSessions returns the most recent sessions ordered by connected_at DESC.
 	// If activeOnly is true, only sessions with no disconnected_at are returned.
 	GetRecentSessions(ctx context.Context, limit int, activeOnly bool) ([]Session, error)