Fix time-off date display and improve UI

Scan datetime columns directly into time.Time instead of strings in the
timeoff store — the intermediate string parse silently failed with
parseTime=true, producing zero-value dates. Display dates with month
names and filter admin's own entry from the volunteer dropdown.

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

web/src/pages/TimeOff.tsx

@@ -157,7 +157,7 @@ export default function TimeOff() {
                 onChange={e => setForm(f => ({ ...f, volunteer_id: Number(e.target.value) }))}
               >
                 <option value={0}>Myself</option>
-                {volunteers.map(v => (
+                {volunteers.filter(v => v.id !== volunteerID).map(v => (
                   <option key={v.id} value={v.id}>{v.name}</option>
                 ))}
               </select>
@@ -226,8 +226,8 @@ export default function TimeOff() {
             {requests.map(r => (
               <tr key={r.id}>
                 {role === 'admin' && <td>{volunteerName(r.volunteer_id)}</td>}
-                <td>{new Date(r.starts_at).toLocaleDateString()}</td>
-                <td>{new Date(r.ends_at).toLocaleDateString()}</td>
+                <td>{new Date(r.starts_at).toLocaleDateString(undefined, { year: 'numeric', month: 'long', day: 'numeric' })}</td>
+                <td>{new Date(r.ends_at).toLocaleDateString(undefined, { year: 'numeric', month: 'long', day: 'numeric' })}</td>
                 <td>{r.reason ?? '—'}</td>
                 <td><span className={statusClass(r.status)}>{r.status}</span></td>
                 <td>