Enhance member activity retrieval by tracking unique activity dates

This commit updates the `getMemberActivities` function to track unique date-activity combinations using a Set, ensuring accurate counting of distinct participation dates. It also refines the logic for handling dates, skipping entries without a date and sorting the dates in descending order. These changes improve the accuracy and clarity of member activity statistics presented to the user.

backend/controllers/memberActivityController.js

@@ -195,6 +195,7 @@ export const getMemberActivities = async (req, res) => {
         const allActivities = [...memberActivities, ...uniqueGroupActivities];
         
         // Group activities by name and count occurrences
+        // Verwende einen Set pro Aktivität, um eindeutige Datum-Aktivität-Kombinationen zu tracken
         const activityMap = new Map();
         
         for (const ma of allActivities) {
@@ -207,6 +208,10 @@ export const getMemberActivities = async (req, res) => {
             const activityCode = activity.code || activity.name; // Verwende Code falls vorhanden, sonst Name
             const date = ma.activity.diaryDate?.date;
             
+            if (!date) {
+                continue; // Überspringe Einträge ohne Datum
+            }
+            
             // Verwende Code als Key, falls vorhanden, sonst Name
             const key = activityCode;
             
@@ -214,18 +219,37 @@ export const getMemberActivities = async (req, res) => {
                 activityMap.set(key, {
                     name: activityName, // Vollständiger Name für Tooltip
                     code: activityCode, // Code/Kürzel für Anzeige
-                    count: 0,
+                    uniqueDates: new Set(), // Set für eindeutige Daten
                     dates: []
                 });
             }
             
             const activityData = activityMap.get(key);
-            activityData.count++;
-            if (date) {
+            // Konvertiere Datum zu String für Set-Vergleich (nur Datum, keine Zeit)
+            const dateString = date instanceof Date 
+                ? date.toISOString().split('T')[0] 
+                : new Date(date).toISOString().split('T')[0];
+            
+            // Füge Datum nur hinzu, wenn es noch nicht vorhanden ist
+            if (!activityData.uniqueDates.has(dateString)) {
+                activityData.uniqueDates.add(dateString);
                 activityData.dates.push(date);
             }
         }
         
+        // Konvertiere Sets zu Arrays und setze count basierend auf eindeutigen Daten
+        activityMap.forEach((activityData, key) => {
+            activityData.count = activityData.uniqueDates.size;
+            // Sortiere Daten (neueste zuerst)
+            activityData.dates.sort((a, b) => {
+                const dateA = new Date(a);
+                const dateB = new Date(b);
+                return dateB - dateA;
+            });
+            // Entferne uniqueDates, da es nicht an Frontend gesendet werden muss
+            delete activityData.uniqueDates;
+        });
+        
         // Convert map to array and sort by count
         const activities = Array.from(activityMap.values())
             .sort((a, b) => b.count - a.count);