fix: prevent double date formatting in email templates

- Remove pre-formatting of dates before passing to email processor
- Let email processor handle all date formatting based on recipient language
- Fix Invalid Date errors by passing raw date values instead of formatted strings
- Remove unused formatDate imports and variables

🤖 Generated with [Claude Code](https://claude.ai/code)

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

backend/src/services/watermarkService.js

@@ -56,30 +56,30 @@ class WatermarkService {
     let left, top;
 
     switch (position) {
-      case 'top-left':
-        left = padding;
-        top = padding;
-        break;
-      case 'top-right':
-        left = imageWidth - watermarkWidth - padding;
-        top = padding;
-        break;
-      case 'bottom-left':
-        left = padding;
-        top = imageHeight - watermarkHeight - padding;
-        break;
-      case 'bottom-right':
-        left = imageWidth - watermarkWidth - padding;
-        top = imageHeight - watermarkHeight - padding;
-        break;
-      case 'center':
-        left = Math.floor((imageWidth - watermarkWidth) / 2);
-        top = Math.floor((imageHeight - watermarkHeight) / 2);
-        break;
-      default:
-        // Default to bottom-right
-        left = imageWidth - watermarkWidth - padding;
-        top = imageHeight - watermarkHeight - padding;
+    case 'top-left':
+      left = padding;
+      top = padding;
+      break;
+    case 'top-right':
+      left = imageWidth - watermarkWidth - padding;
+      top = padding;
+      break;
+    case 'bottom-left':
+      left = padding;
+      top = imageHeight - watermarkHeight - padding;
+      break;
+    case 'bottom-right':
+      left = imageWidth - watermarkWidth - padding;
+      top = imageHeight - watermarkHeight - padding;
+      break;
+    case 'center':
+      left = Math.floor((imageWidth - watermarkWidth) / 2);
+      top = Math.floor((imageHeight - watermarkHeight) / 2);
+      break;
+    default:
+      // Default to bottom-right
+      left = imageWidth - watermarkWidth - padding;
+      top = imageHeight - watermarkHeight - padding;
     }
 
     return { left: Math.max(0, left), top: Math.max(0, top) };