Switch all user-facing time displays to 12-hour MM-DD-YYYY format

Consistently format dates and times across all templates and API
handlers using MM-DD-YYYY with 12-hour clock (03:04 PM):

- analytics.go: date keys, lastSync, lastRead timestamps
- progress.go: lastUpdated timestamp in GetAllProgress
- book_detail.templ: LastReadAt, DatePublished
- book_detail_modals.templ: progress sync timestamps, LastReadAt
- devices.templ: LastSync, LastSeen
- conflicts.templ: CreatedAt
- admin_users.templ: user CreatedAt date

templates/book_detail_modals.templ

@@ -65,7 +65,7 @@ templ ProgressSyncModal(book handlers.MediaDetail) {
 										{ source }
 									</span>
 									<p class="text-xs" style="color: var(--text-secondary);">
-										{ data.Timestamp.Format("2006-01-02 15:04:05") }
+										{ data.Timestamp.Format("01-02-2006 03:04 PM:05") }
 									</p>
 								</div>
 								<div class="text-right">
@@ -110,7 +110,7 @@ templ ProgressSyncModal(book handlers.MediaDetail) {
 					}
 					if book.ReadingProgress.LastReadAt.Valid {
 						<p class="text-sm mt-2" style="color: var(--text-secondary);">
-							Last read: { book.ReadingProgress.LastReadAt.Time.Format("2006-01-02 15:04") }
+							Last read: { book.ReadingProgress.LastReadAt.Time.Format("01-02-2006 03:04 PM") }
 						</p>
 					}
 				</div>