fix(frontend): hide calendar popups on empty dates

Keep race popovers limited to dates with events so empty days no longer show misleading hover details.

Made-with: Cursor

frontend/src/components/RacesCalendar.tsx

@@ -120,7 +120,7 @@ function CalendarMonthBlock(props: {
               className={`races-cal__cell${hasRaces ? " races-cal__cell--has-race" : ""}${isOpen ? " races-cal__cell--open" : ""}`}
               onMouseEnter={() => {
                 cancelClose();
-                setOpenYmd(ymd);
+                setOpenYmd(hasRaces ? ymd : null);
               }}
               onMouseLeave={scheduleClose}
             >
@@ -132,7 +132,7 @@ function CalendarMonthBlock(props: {
                 }}
                 onFocus={() => {
                   cancelClose();
-                  setOpenYmd(ymd);
+                  setOpenYmd(hasRaces ? ymd : null);
                 }}
                 onBlur={(e) => {
                   const next = e.relatedTarget as Node | null;
@@ -144,7 +144,7 @@ function CalendarMonthBlock(props: {
               >
                 {day}
               </button>
-              {isOpen ? (
+              {isOpen && hasRaces ? (
                 <DayPopover
                   ymd={ymd}
                   races={dayRaces}
@@ -187,7 +187,7 @@ export function RacesCalendar(props: RacesCalendarProps): JSX.Element {
 
   return (
     <div className="races-cal">
-      <p className="races-cal__hint">Наведите на дату — краткая информация. Клик — страница дня.</p>
+      <p className="races-cal__hint">Наведите на дату с забегом — краткая информация. Клик — страница дня.</p>
       {focusedMonthIndex === null || Number.isNaN(focusedMonthIndex) ? (
         <div className="races-cal__year">
           {MONTH_NAMES_RU_SHORT.map((_, mi) => (