Add missing salesStatistics API function

app/Http/Controllers/InvoiceController.php

@@ -48,9 +48,8 @@ public function summaryAll()
 
     public function summaryThisYear()
     {
-	$dt = new DateTime('first day of january this year');
         $invoices = Invoice::select()
-            ->where('invoice_date', '>=', $dt->format('Y-m-d'))
+            ->where('invoice_date', '>=', (new DateTime('first day of january this year')->format('Y-m-d')))
             ->orderBy('invoice_date', 'asc')
             ->orderByRaw("CAST(SUBSTRING(nr, 4) AS UNSIGNED) ASC")
             ->get();
@@ -62,9 +61,8 @@ public function summaryThisYear()
 
     public function summaryBeforeThisYear()
     {
-	$dt = new DateTime('first day of january this year');
         $invoices = Invoice::select()
-            ->where('invoice_date', '<', $dt->format('Y-m-d'))
+            ->where('invoice_date', '<', (new DateTime('first day of january this year')->format('Y-m-d')))
             ->orderBy('invoice_date', 'asc')
             ->orderByRaw("CAST(SUBSTRING(nr, 4) AS UNSIGNED) ASC")
             ->get();
@@ -116,6 +114,66 @@ public static function single($id)
         return ApiDataTransformer::snakeToCamel($invoiceArray);
     }
 
+    /**
+     * Get yearly statistics for invoices
+     */
+    public function salesStatistics()
+    {
+        $currentYear = date('Y');
+
+        // Basis-Abfrage für das aktuelle Jahr
+        $invoicesQuery = Invoice::whereYear('invoice_date', $currentYear);
+
+        // Gesamtumsatz (alle außer cancelled)
+        $totalRevenue = $invoicesQuery->clone()
+            ->where('payment_status', '!=', 'cancelled')
+            ->sum('total_amount');
+
+        // Bezahlt (paid)
+        $paid = $invoicesQuery->clone()
+            ->where('payment_status', 'paid')
+            ->sum('total_amount');
+
+        // Noch nicht gestellt (draft)
+        $draft = $invoicesQuery->clone()
+            ->where('payment_status', 'draft')
+            ->sum('total_amount');
+
+        // Offene Rechnungen (issued)
+        $issued = $invoicesQuery->clone()
+            ->where('payment_status', 'issued')
+            ->sum('total_amount');
+
+        // Fällige Rechnungen (due)
+        $due = $invoicesQuery->clone()
+            ->where('payment_status', 'due')
+            ->sum('total_amount');
+
+        // Gemahnte Rechnungen (reminded)
+        $reminded = $invoicesQuery->clone()
+            ->where('payment_status', 'reminded')
+            ->sum('total_amount');
+
+        // Statistikdaten zusammenstellen
+        $statistics = [
+            'year' => $currentYear,
+            'totalRevenue' => $totalRevenue,
+            'paid' => $paid,
+            'paidPercent' => round(($paid / $totalRevenue) * 100, 2),
+            'draft' => $draft,
+            'draftPercent' => round(($draft / $totalRevenue) * 100, 2),
+            'issued' => $issued,
+            'issuedPercent' => round(($issued / $totalRevenue) * 100, 2),
+            'due' => $due,
+            'duePercent' => round(($due / $totalRevenue) * 100, 2),
+            'reminded' => $reminded,
+            'remindedPercent' => round(($reminded / $totalRevenue) * 100, 2),
+        ];
+
+        // Daten in camelCase umwandeln
+        return ApiDataTransformer::snakeToCamel($statistics);
+    }
+
 
     public function preview($id)
     {