Add voucher-line party (تفصیل) and allow cache-control CORS headers.

Supports accounting journal detail parties and preflight from the Vite client that sends Cache-Control/Pragma.

Co-authored-by: Cursor <cursoragent@cursor.com>

accounting/models.py

@@ -137,6 +137,14 @@ class VoucherLine(models.Model):
     id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
     voucher = models.ForeignKey(Voucher, on_delete=models.CASCADE, related_name='lines')
     account = models.ForeignKey(Account, on_delete=models.PROTECT, related_name='voucher_lines')
+    # تفصیل / طرف حساب — who the line is with (optional for non-party accounts)
+    party = models.ForeignKey(
+        Party,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        related_name='voucher_lines',
+    )
     description = models.CharField(max_length=255, blank=True, default='')
     debit = models.FloatField(default=0)
     credit = models.FloatField(default=0)