Initial commit: CleanPlate shared Dart package

Domain models, enums, constants, validators shared between frontend and backend.

test/cleanplate_shared_test.dart

@@ -0,0 +1,46 @@
+import 'package:cleanplate_shared/cleanplate_shared.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('RecipeValidator', () {
+    test('validateTitle returns null for valid title', () {
+      expect(RecipeValidator.validateTitle('My Recipe'), isNull);
+    });
+
+    test('validateTitle returns error for empty title', () {
+      expect(RecipeValidator.validateTitle(''), isNotNull);
+    });
+
+    test('validateServings returns null for valid servings', () {
+      expect(RecipeValidator.validateServings(4), isNull);
+    });
+
+    test('validateServings returns error for zero servings', () {
+      expect(RecipeValidator.validateServings(0), isNotNull);
+    });
+
+    test('validateRating returns null for valid rating', () {
+      expect(RecipeValidator.validateRating(5), isNull);
+    });
+
+    test('validateRating returns error for out-of-range rating', () {
+      expect(RecipeValidator.validateRating(6), isNotNull);
+    });
+  });
+
+  group('DietType', () {
+    test('displayName returns correct value', () {
+      expect(DietType.vegan.displayName, equals('Vegan'));
+    });
+  });
+
+  group('ApiConstants', () {
+    test('basePath includes version', () {
+      expect(ApiConstants.basePath, equals('/api/v1'));
+    });
+
+    test('recipe path includes id', () {
+      expect(ApiConstants.recipe('abc'), equals('/api/v1/recipes/abc'));
+    });
+  });
+}