Attendance: detect rest day in enrich → render 休息 instead of 缺勤

When roster says the shift rests on a given weekday (e.g. Sunday for S2/S3),
the employee wasn't scheduled to work. Import still marks the record
status_code='missing' because no shift times were available, but the
right user-facing label is '休息' not '缺勤'.

Enrich now: if status_code='missing' and get_shift_schedule_full returns
None (shift defined no schedule for that weekday), override to
status_code='rest' / status_text='休息'.

Added '休息' to the basic-status vocabulary: dropdown option, filter
condition, StatusBadge (slate grey + coffee icon), and row highlight.

frontend/src/pages/attendance/List.jsx

@@ -99,6 +99,7 @@ export default function AttendanceList() {
       return 'bg-orange-50 hover:bg-orange-100'
     }
     if (c === 'missing') return 'bg-gray-100 hover:bg-gray-200'
+    if (c === 'rest') return 'bg-slate-50 hover:bg-slate-100'
     if (c === 'holiday') return 'bg-indigo-50 hover:bg-indigo-100'
     if (['al', 'sl', 'cl', 'mixed_leave'].includes(c)) return 'bg-violet-50 hover:bg-violet-100'
     return 'hover:bg-slate-50'