Make remaining date inputs Safari-safe (uncontrolled)

Attendance filter, gradebook assignment date, and tuition entry date now use
defaultValue (with a remount key where the field resets after submit).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/routes/_authenticated/attendance.tsx

@@ -69,7 +69,7 @@ function AttendancePage() {
             <SelectContent>{(classes ?? []).map((c) => <SelectItem key={c.id} value={c.id}>{c.name}</SelectItem>)}</SelectContent>
           </Select>
         </div>
-        <Input type="date" className="w-44" value={date} onChange={(e) => setDate(e.target.value)} />
+        <Input type="date" className="w-44" defaultValue={date} onChange={(e) => setDate(e.target.value)} />
       </div>
 
       {classId && (