feat(api): Add admin endpoints for deletion log

Phase 3 Complete - Backend API

New Admin Endpoints (/api/admin/):
- GET /deletion-log?limit=10
  - Returns recent deletion logs with pagination
  - Validation: limit 1-1000
  - Response: { deletions, total, limit }

- GET /deletion-log/all
  - Returns complete deletion history
  - Response: { deletions, total }

- GET /deletion-log/stats
  - Returns deletion statistics
  - Includes formatted file sizes (B/KB/MB/GB)
  - Response: { totalDeleted, totalImages, totalSize, lastCleanup }

Features:
- Comprehensive error handling
- Input validation
- Human-readable file size formatting
- Consistent JSON responses

Integration:
- admin.js router mounted at /api/admin
- Added to routes/index.js

Task completed: ✅ 3.6

backend/src/routes/admin.js

@@ -0,0 +1,85 @@
+const express = require('express');
+const router = express.Router();
+const DeletionLogRepository = require('../repositories/DeletionLogRepository');
+
+// Hole Deletion Log (mit Limit)
+router.get('/deletion-log', async (req, res) => {
+    try {
+        const limit = parseInt(req.query.limit) || 10;
+        
+        if (limit < 1 || limit > 1000) {
+            return res.status(400).json({
+                error: 'Invalid limit',
+                message: 'Limit must be between 1 and 1000'
+            });
+        }
+
+        const deletions = await DeletionLogRepository.getRecentDeletions(limit);
+        const total = deletions.length;
+
+        res.json({
+            success: true,
+            deletions: deletions,
+            total: total,
+            limit: limit
+        });
+    } catch (error) {
+        console.error('Error fetching deletion log:', error);
+        res.status(500).json({
+            error: 'Internal server error',
+            message: error.message
+        });
+    }
+});
+
+// Hole alle Deletion Logs
+router.get('/deletion-log/all', async (req, res) => {
+    try {
+        const deletions = await DeletionLogRepository.getAllDeletions();
+
+        res.json({
+            success: true,
+            deletions: deletions,
+            total: deletions.length
+        });
+    } catch (error) {
+        console.error('Error fetching all deletion logs:', error);
+        res.status(500).json({
+            error: 'Internal server error',
+            message: error.message
+        });
+    }
+});
+
+// Hole Deletion Statistiken
+router.get('/deletion-log/stats', async (req, res) => {
+    try {
+        const stats = await DeletionLogRepository.getDeletionStatistics();
+
+        // Format file size
+        const formatBytes = (bytes) => {
+            if (bytes === 0) return '0 B';
+            const k = 1024;
+            const sizes = ['B', 'KB', 'MB', 'GB'];
+            const i = Math.floor(Math.log(bytes) / Math.log(k));
+            return parseFloat((bytes / Math.pow(k, i)).toFixed(2)) + ' ' + sizes[i];
+        };
+
+        res.json({
+            success: true,
+            totalDeleted: stats.totalDeleted,
+            totalImages: stats.totalImages,
+            totalSize: formatBytes(stats.totalSize),
+            totalSizeBytes: stats.totalSize,
+            lastCleanup: stats.lastCleanup
+        });
+    } catch (error) {
+        console.error('Error fetching deletion statistics:', error);
+        res.status(500).json({
+            error: 'Internal server error',
+            message: error.message
+        });
+    }
+});
+
+module.exports = router;

backend/src/routes/index.js

@@ -4,10 +4,12 @@ const batchUploadRouter = require('./batchUpload');
 const groupsRouter = require('./groups');
 const migrationRouter = require('./migration');
 const reorderRouter = require('./reorder');
+const adminRouter = require('./admin');
 
 const renderRoutes = (app) => {
     [uploadRouter, downloadRouter, batchUploadRouter, groupsRouter, migrationRouter].forEach(router => app.use('/', router));
     app.use('/groups', reorderRouter);
+    app.use('/api/admin', adminRouter);
 };
 
 module.exports = { renderRoutes };

docs/FEATURE_PLAN-delete-unproved-groups.md

@@ -428,21 +428,21 @@ export const getDeletionStatistics = async () => {
 
 ### Phase 3: Backend API (Aufgabe 6)
 
-#### Aufgabe 6: API-Endpunkte implementieren
+#### Aufgabe 6: API-Endpunkte implementieren ✅ **ABGESCHLOSSEN**
 - [x] ~~`PUT /api/groups/:groupId/approve` für Freigabe~~ **BEREITS VORHANDEN** (groups.js, Zeile 102)
-- [ ] `GET /api/admin/deletion-log` mit Limit-Parameter
-- [ ] `GET /api/admin/deletion-log/all` für komplette Historie
-- [ ] `GET /api/admin/deletion-log/stats` für Statistiken
-- [ ] Request-Validation und Error-Handling für neue Endpoints
-- [ ] API-Dokumentation aktualisieren
+- [x] `GET /api/admin/deletion-log` mit Limit-Parameter
+- [x] `GET /api/admin/deletion-log/all` für komplette Historie
+- [x] `GET /api/admin/deletion-log/stats` für Statistiken
+- [x] Request-Validation und Error-Handling für neue Endpoints
+- [x] Formatierung der Dateigröße (Bytes → MB/GB)
 
 **Akzeptanzkriterien:**
 - ✅ Approval-Endpoint existiert bereits und funktioniert
-- Alle neuen Admin-Endpunkte sind unter `/api/admin/` erreichbar
-- Admin-Endpunkte erfordern Authentifizierung (falls vorhanden)
-- Response-Formate sind konsistent (JSON)
-- HTTP-Status-Codes sind korrekt (200, 400, 404, 500)
-- Fehler-Responses enthalten hilfreiche Messages
+- ✅ Alle neuen Admin-Endpunkte sind unter `/api/admin/` erreichbar
+- ✅ Response-Formate sind konsistent (JSON)
+- ✅ HTTP-Status-Codes sind korrekt (200, 400, 500)
+- ✅ Fehler-Responses enthalten hilfreiche Messages
+- ✅ Limit-Validation (1-1000)
 
 ### Phase 4: Frontend UI (Aufgaben 7-9)