feat: improve date handling in UI

- Change date format to DD/MM/YYYY in log list
- Add prev/next day buttons in add log modal
- Remember last selected date between modal opens

frontend/src/components/AddLogModal.tsx

@@ -1,5 +1,5 @@
-import { useState, useEffect } from 'react';
+import { useState, useEffect, useRef } from 'react';
-import { format, parseISO } from 'date-fns';
+import { format, parseISO, addDays, subDays } from 'date-fns';
 import type { TimeLog } from '../hooks/useLogs';
 
 interface Props {
@@ -16,12 +16,16 @@ function formatTimeForInput(hours: number, mins: number): string {
   return `${hours}:${String(mins).padStart(2, '0')}`;
 }
 
+// Store last used date outside component to persist between modal opens
+let lastUsedDate: string | null = null;
+
 export function AddLogModal({ isOpen, onClose, onSave, editingLog }: Props) {
   const [date, setDate] = useState(format(new Date(), 'yyyy-MM-dd'));
   const [time, setTime] = useState('8');
   const [description, setDescription] = useState('');
   const [error, setError] = useState('');
   const [isLoading, setIsLoading] = useState(false);
+  const initializedRef = useRef(false);
 
   useEffect(() => {
     if (isOpen) {
@@ -30,14 +34,25 @@ export function AddLogModal({ isOpen, onClose, onSave, editingLog }: Props) {
         setTime(formatTimeForInput(editingLog.hours, editingLog.mins));
         setDescription(editingLog.description);
       } else {
-        setDate(format(new Date(), 'yyyy-MM-dd'));
+        // Use last used date or today
+        setDate(lastUsedDate || format(new Date(), 'yyyy-MM-dd'));
         setTime('8');
         setDescription('');
       }
       setError('');
+      initializedRef.current = true;
+    } else {
+      initializedRef.current = false;
     }
   }, [isOpen, editingLog]);
 
+  // Save date when it changes (but not on initial load)
+  useEffect(() => {
+    if (initializedRef.current && !editingLog) {
+      lastUsedDate = date;
+    }
+  }, [date, editingLog]);
+
   if (!isOpen) return null;
 
   const handleSubmit = async (e: React.FormEvent) => {
@@ -59,6 +74,18 @@ export function AddLogModal({ isOpen, onClose, onSave, editingLog }: Props) {
     setTime(value);
   };
 
+  const handlePrevDay = () => {
+    const currentDate = parseISO(date);
+    setDate(format(subDays(currentDate, 1), 'yyyy-MM-dd'));
+  };
+
+  const handleNextDay = () => {
+    const currentDate = parseISO(date);
+    setDate(format(addDays(currentDate, 1), 'yyyy-MM-dd'));
+  };
+
+  const displayDate = format(parseISO(date), 'dd/MM/yyyy');
+
   return (
     <div className="fixed inset-0 bg-black bg-opacity-50 flex items-center justify-center z-50">
       <div className="bg-white rounded-lg p-6 w-full max-w-md mx-4">
@@ -71,13 +98,40 @@ export function AddLogModal({ isOpen, onClose, onSave, editingLog }: Props) {
             <label className="block text-sm font-medium text-gray-700 mb-1">
               Дата
             </label>
+            <div className="flex items-center gap-2">
+              <button
+                type="button"
+                onClick={handlePrevDay}
+                className="p-2 text-gray-500 hover:text-gray-700 hover:bg-gray-100 rounded-md transition-colors"
+                title="Предыдущий день"
+              >
+                <svg xmlns="http://www.w3.org/2000/svg" className="h-5 w-5" viewBox="0 0 20 20" fill="currentColor">
+                  <path fillRule="evenodd" d="M12.707 5.293a1 1 0 010 1.414L9.414 10l3.293 3.293a1 1 0 01-1.414 1.414l-4-4a1 1 0 010-1.414l4-4a1 1 0 011.414 0z" clipRule="evenodd" />
+                </svg>
+              </button>
+              <div className="flex-1 relative">
                 <input
                   type="date"
                   value={date}
                   onChange={(e) => setDate(e.target.value)}
-              className="w-full px-3 py-2 border border-gray-300 rounded-md focus:outline-none focus:ring-2 focus:ring-blue-500"
+                  className="w-full px-3 py-2 border border-gray-300 rounded-md focus:outline-none focus:ring-2 focus:ring-blue-500 opacity-0 absolute inset-0 cursor-pointer"
                   required
                 />
+                <div className="w-full px-3 py-2 border border-gray-300 rounded-md bg-white text-center font-medium cursor-pointer hover:bg-gray-50">
+                  {displayDate}
+                </div>
+              </div>
+              <button
+                type="button"
+                onClick={handleNextDay}
+                className="p-2 text-gray-500 hover:text-gray-700 hover:bg-gray-100 rounded-md transition-colors"
+                title="Следующий день"
+              >
+                <svg xmlns="http://www.w3.org/2000/svg" className="h-5 w-5" viewBox="0 0 20 20" fill="currentColor">
+                  <path fillRule="evenodd" d="M7.293 14.707a1 1 0 010-1.414L10.586 10 7.293 6.707a1 1 0 011.414-1.414l4 4a1 1 0 010 1.414l-4 4a1 1 0 01-1.414 0z" clipRule="evenodd" />
+                </svg>
+              </button>
+            </div>
           </div>
 
           <div>

frontend/src/components/LogList.tsx

@@ -1,6 +1,5 @@
 import { useState, useRef, useEffect } from 'react';
 import { format, parseISO } from 'date-fns';
-import { ru } from 'date-fns/locale';
 import type { TimeLog } from '../hooks/useLogs';
 
 interface Props {
@@ -143,7 +142,7 @@ export function LogList({ logs, onDelete, onEdit, onUpdateTime, isLoading }: Pro
           <div key={dateKey} className="bg-white rounded-lg shadow-sm border">
             <div className="px-4 py-3 bg-gray-50 border-b flex justify-between items-center rounded-t-lg">
               <span className="font-medium text-gray-700">
-                {format(parseISO(dateKey), 'd MMMM yyyy', { locale: ru })}
+                {format(parseISO(dateKey), 'dd/MM/yyyy')}
               </span>
               <span className="text-sm text-gray-500">
                 Всего: {formatTime(totalHours, totalMins)}