feat: implement base recipe references with customizable ingredients and instructions

Add comprehensive base recipe system allowing recipes to reference other recipes dynamically. References can include custom items before/after the base recipe content and render as unified lists.

Features:
- Mark recipes as base recipes with isBaseRecipe flag
- Insert base recipe references at any position in ingredients/instructions
- Add custom items before/after referenced content (itemsBefore/itemsAfter, stepsBefore/stepsAfter)
- Combined rendering displays all items in single unified lists
- Full edit/remove functionality for additional items with modal reuse
- Empty item validation prevents accidental blank entries
- HTML rendering in section titles for proper <wbr> and &shy; support
- Reference links in section headings with multiplier preservation
- Subtle hover effects (2% scale) on add buttons
- Translation support for all reference fields
- Deletion handling expands references before removing base recipes

src/routes/api/rezepte/base-recipes/+server.ts

@@ -0,0 +1,16 @@
+import type { RequestHandler } from '@sveltejs/kit';
+import { Recipe } from '../../../../models/Recipe';
+import { dbConnect } from '../../../../utils/db';
+import { json } from '@sveltejs/kit';
+
+// GET: List all base recipes for selector UI
+export const GET: RequestHandler = async () => {
+	await dbConnect();
+
+	const baseRecipes = await Recipe.find({ isBaseRecipe: true })
+		.select('_id short_name name category icon')
+		.sort({ name: 1 })
+		.lean();
+
+	return json(baseRecipes);
+};

src/routes/api/rezepte/check-references/[id]/+server.ts

@@ -0,0 +1,21 @@
+import type { RequestHandler } from '@sveltejs/kit';
+import { Recipe } from '../../../../../models/Recipe';
+import { dbConnect } from '../../../../../utils/db';
+import { json } from '@sveltejs/kit';
+
+// GET: Check which recipes reference this recipe
+export const GET: RequestHandler = async ({ params }) => {
+	await dbConnect();
+
+	const referencingRecipes = await Recipe.find({
+		$or: [
+			{ 'ingredients.baseRecipeRef': params.id },
+			{ 'instructions.baseRecipeRef': params.id }
+		]
+	}).select('short_name name').lean();
+
+	return json({
+		isReferenced: referencingRecipes.length > 0,
+		references: referencingRecipes
+	});
+};

src/routes/api/rezepte/delete/+server.ts

@@ -21,6 +21,45 @@ export const POST: RequestHandler = async ({request, locals}) => {
 		throw error(404, "Recipe not found");
 	}
 
+	// Check if this recipe is referenced by others
+	const referencingRecipes = await Recipe.find({
+		$or: [
+			{ 'ingredients.baseRecipeRef': recipe._id },
+			{ 'instructions.baseRecipeRef': recipe._id }
+		]
+	});
+
+	// Expand all references into regular content before deletion
+	for (const depRecipe of referencingRecipes) {
+		// Expand ingredient references
+		if (depRecipe.ingredients) {
+			depRecipe.ingredients = depRecipe.ingredients.flatMap((item: any) => {
+				if (item.type === 'reference' && item.baseRecipeRef && item.baseRecipeRef.equals(recipe._id)) {
+					if (item.includeIngredients && recipe.ingredients) {
+						return recipe.ingredients.filter((i: any) => i.type === 'section' || !i.type);
+					}
+					return [];
+				}
+				return [item];
+			});
+		}
+
+		// Expand instruction references
+		if (depRecipe.instructions) {
+			depRecipe.instructions = depRecipe.instructions.flatMap((item: any) => {
+				if (item.type === 'reference' && item.baseRecipeRef && item.baseRecipeRef.equals(recipe._id)) {
+					if (item.includeInstructions && recipe.instructions) {
+						return recipe.instructions.filter((i: any) => i.type === 'section' || !i.type);
+					}
+					return [];
+				}
+				return [item];
+			});
+		}
+
+		await depRecipe.save();
+	}
+
 	// Remove this recipe from all users' favorites
 	await UserFavorites.updateMany(
 		{ favorites: recipe._id },

src/routes/api/rezepte/items/[name]/+server.ts

@@ -6,11 +6,40 @@ import { error } from '@sveltejs/kit';
 
 export const GET: RequestHandler = async ({params}) => {
   await dbConnect();
-  let recipe = (await Recipe.findOne({ short_name: params.name}).lean()) as RecipeModelType[];
+  let recipe = await Recipe.findOne({ short_name: params.name})
+    .populate({
+      path: 'ingredients.baseRecipeRef',
+      select: 'short_name name ingredients translations'
+    })
+    .populate({
+      path: 'instructions.baseRecipeRef',
+      select: 'short_name name instructions translations'
+    })
+    .lean() as RecipeModelType[];
 
   recipe = JSON.parse(JSON.stringify(recipe));
   if(recipe == null){
 	throw error(404, "Recipe not found")
   }
+
+  // Map populated refs to resolvedRecipe field
+  if (recipe?.ingredients) {
+    recipe.ingredients = recipe.ingredients.map((item: any) => {
+      if (item.type === 'reference' && item.baseRecipeRef) {
+        return { ...item, resolvedRecipe: item.baseRecipeRef };
+      }
+      return item;
+    });
+  }
+
+  if (recipe?.instructions) {
+    recipe.instructions = recipe.instructions.map((item: any) => {
+      if (item.type === 'reference' && item.baseRecipeRef) {
+        return { ...item, resolvedRecipe: item.baseRecipeRef };
+      }
+      return item;
+    });
+  }
+
   return json(recipe);
 };