feat: Add receipt import functionality with file upload and parsing

- Implemented receipt file upload in ImportRepository with multipart request handling.
- Created ParsedReceiptItem model for parsed receipt data.
- Added ReceiptImportTab for user interface to upload and review receipts.
- Updated ImportScreen to include the new ReceiptImportTab alongside RecipeImportTab.
- Introduced flutter_bootstrap.js and index.html for web app initialization.
- Added wimp.wasm and flutter.js for enhanced web performance and capabilities.

flutter/lib/features/import/domain/parsed_receipt_item.dart

@@ -0,0 +1,27 @@
+/// Model for a parsed receipt item from the receipt import API.
+class ParsedReceiptItem {
+  final String rawName;
+  final double? quantity;
+  final String? unit;
+  final String? suggestedProductId;
+  final String? suggestedProductName;
+  final String? categorySuggestion;
+
+  ParsedReceiptItem({
+    required this.rawName,
+    this.quantity,
+    this.unit,
+    this.suggestedProductId,
+    this.suggestedProductName,
+    this.categorySuggestion,
+  });
+
+  factory ParsedReceiptItem.fromJson(Map<String, dynamic> json) => ParsedReceiptItem(
+        rawName: json['rawName'] as String,
+        quantity: (json['quantity'] as num?)?.toDouble(),
+        unit: json['unit'] as String?,
+        suggestedProductId: json['suggestedProductId'] as String?,
+        suggestedProductName: json['suggestedProductName'] as String?,
+        categorySuggestion: json['categorySuggestion'] as String?,
+      );
+}