refactor: sjednoceni zdroje casu na MySQL NOW() + audit log cleanup a UI

- attendance handlery pouzivaji getDbNow() misto PHP date()
- nova helper funkce getDbNow() v AttendanceHelpers.php
- audit log: cleanup endpoint (POST) s volbou stari zaznamu
- audit log: filtry na jednom radku
- dashboard: aktivita prejmenovana na Audit log s odkazem

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

api/includes/AttendanceHelpers.php

@@ -6,6 +6,21 @@
 
 declare(strict_types=1);
 
+/**
+ * Vraci aktualni cas a datum z MySQL (jednotny zdroj casu)
+ * @return array{now: string, today: string, year: int, month: int}
+ */
+function getDbNow(PDO $pdo): array
+{
+    $row = $pdo->query("SELECT NOW() AS now, CURDATE() AS today, YEAR(NOW()) AS y, MONTH(NOW()) AS m")->fetch();
+    return [
+        'now' => $row['now'],
+        'today' => $row['today'],
+        'year' => (int)$row['y'],
+        'month' => (int)$row['m'],
+    ];
+}
+
 function roundUpTo15Minutes(string $datetime): string
 {
     $timestamp = strtotime($datetime);
@@ -327,15 +342,14 @@ function addFundDataToUserTotals(PDO $pdo, array &$userTotals, int $year, int $m
     }
     unset($ut);
 
-    $today = date('Y-m-d');
     $stmt = $pdo->prepare("
         SELECT DISTINCT user_id FROM attendance
-        WHERE shift_date = ?
+        WHERE shift_date = CURDATE()
         AND arrival_time IS NOT NULL
         AND departure_time IS NULL
         AND (leave_type IS NULL OR leave_type = 'work')
     ");
-    $stmt->execute([$today]);
+    $stmt->execute();
     $workingNow = $stmt->fetchAll(PDO::FETCH_COLUMN);
     foreach ($workingNow as $uid) {
         if (isset($userTotals[$uid])) {