feat(ui): use timezone-aware time formatting across all templates

Replace hardcoded .Format() calls with FormatInTimezone() and
FormatTimestamptzInTimezone() helpers so all timestamps display in
the user's selected timezone.

Changes:
- book_detail.templ: remove incorrect templates. package prefix
- book_detail_modals.templ: add User param to ProgressSyncModal so
  timezone is available; convert Timestamp to FormatInTimezone()
- devices.templ: convert LastSync and LastSeen to FormatInTimezone()
- conflicts.templ: convert CreatedAt to FormatInTimezone()
- admin_users.templ: convert CreatedAt to FormatInTimezone() using
  currentUser.Timezone

Note: DatePublished is kept as a plain date format (MM-DD-YYYY) since
it is a pgtype.Date, not a timestamp, and does not need timezone
conversion.

templates/devices.templ

@@ -80,7 +80,7 @@ templ Devices(user User, devices []handlers.DeviceInfo, pendingRegistrations []P
 										<div class="flex justify-between">
 											<span style="color: var(--text-secondary)">Last Sync</span>
 											if device.LastSync != nil {
-												<span style="color: var(--text-primary)">{ device.LastSync.Format("01-02-2006 03:04 PM") }</span>
+												<span style="color: var(--text-primary)">{ FormatInTimezone(*device.LastSync, user.Timezone) }</span>
 											} else {
 												<span style="color: var(--text-primary)">Never</span>
 											}
@@ -88,7 +88,7 @@ templ Devices(user User, devices []handlers.DeviceInfo, pendingRegistrations []P
 										<div class="flex justify-between">
 											<span style="color: var(--text-secondary)">Last Seen</span>
 											if device.LastSeen != nil {
-												<span style="color: var(--text-primary)">{ device.LastSeen.Format("01-02-2006 03:04 PM") }</span>
+												<span style="color: var(--text-primary)">{ FormatInTimezone(*device.LastSeen, user.Timezone) }</span>
 											} else {
 												<span style="color: var(--text-primary)">Never</span>
 											}