feat(recipes): add recipe visibility and sharing features

- Implemented functionality to set recipe visibility (public/private) with appropriate checks for user permissions.
- Added ability to share recipes with other users, including validation for existing users and permissions.
- Introduced new DTOs for setting visibility and sharing recipes.
- Updated RecipesController and RecipesService to handle new endpoints for visibility and sharing.
- Enhanced inventory preview to consider user permissions and shared recipes.
- Updated front-end to support new sharing and visibility features, including UI changes for recipe detail and admin user management.

flutter/lib/features/recipes/data/recipe_repository.dart

@@ -94,6 +94,65 @@ class RecipeRepository {
     }
   }
 
+  Future<Recipe> setRecipeVisibility(int id, {required bool isPublic, String? token}) async {
+    try {
+      final data = await _api.patchJson(
+        RecipeApiPaths.setVisibility(id),
+        body: {'isPublic': isPublic},
+        token: token,
+      );
+      if (data is! Map<String, dynamic>) {
+        throw const ApiException(
+            type: ApiErrorType.unknown, message: 'Ogiltigt svar från servern.');
+      }
+      return Recipe.fromJson(data);
+    } on ApiException {
+      rethrow;
+    } catch (_) {
+      throw const ApiException(
+          type: ApiErrorType.network, message: 'Kunde inte uppdatera synlighet.');
+    }
+  }
+
+  Future<Recipe> shareRecipeWithUsername(int id, {required String username, String? token}) async {
+    try {
+      final data = await _api.postJson(
+        RecipeApiPaths.share(id),
+        body: {'username': username},
+        token: token,
+      );
+      if (data is! Map<String, dynamic>) {
+        throw const ApiException(
+            type: ApiErrorType.unknown, message: 'Ogiltigt svar från servern.');
+      }
+      return Recipe.fromJson(data);
+    } on ApiException {
+      rethrow;
+    } catch (_) {
+      throw const ApiException(
+          type: ApiErrorType.network, message: 'Kunde inte dela receptet.');
+    }
+  }
+
+  Future<Recipe> unshareRecipeWithUsername(int id, {required String username, String? token}) async {
+    try {
+      final data = await _api.deleteJson(
+        RecipeApiPaths.unshare(id, username),
+        token: token,
+      );
+      if (data is! Map<String, dynamic>) {
+        throw const ApiException(
+            type: ApiErrorType.unknown, message: 'Ogiltigt svar från servern.');
+      }
+      return Recipe.fromJson(data);
+    } on ApiException {
+      rethrow;
+    } catch (_) {
+      throw const ApiException(
+          type: ApiErrorType.network, message: 'Kunde inte ta bort delning.');
+    }
+  }
+
   Future<InventoryPreview> fetchInventoryPreview(int id,
       {String? token}) async {
     try {