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

internal/handlers/progress.go

@@ -306,7 +306,7 @@ func (h *Handler) GetAllProgress(c *echo.Context) error {
 
 		lastUpdated := ""
 		if progress.LastReadAt.Valid {
-			lastUpdated = progress.LastReadAt.Time.Format("2006-01-02 15:04")
+			lastUpdated = progress.LastReadAt.Time.Format("01-02-2006 03:04 PM")
 		}
 
 		progressList = append(progressList, ProgressWithMedia{