add English translation support for recipes with DeepL integration

- Add embedded translations schema to Recipe model with English support
- Create DeepL translation service with batch translation and change detection
- Build translation approval UI with side-by-side editing for all recipe fields
- Integrate translation workflow into add/edit pages with field comparison
- Create complete English recipe routes at /recipes/* mirroring German structure
- Add language switcher component with hreflang SEO tags
- Support image loading from German short_name for English recipes
- Add English API endpoints for all recipe filters (category, tag, icon, season)
- Include layout with English navigation header for all recipe subroutes

src/models/Recipe.ts

@@ -39,7 +39,53 @@ const RecipeSchema = new mongoose.Schema(
      		      steps: [String]}],
      preamble : String,
      addendum : String,
+
+     // English translations
+     translations: {
+       en: {
+         short_name: {type: String},  // English slug for URLs
+         name: {type: String},
+         description: {type: String},
+         preamble: {type: String},
+         addendum: {type: String},
+         note: {type: String},
+         category: {type: String},
+         tags: [String],
+         ingredients: [{
+           name: {type: String, default: ""},
+           list: [{
+             name: {type: String, default: ""},
+             unit: String,
+             amount: String,
+           }]
+         }],
+         instructions: [{
+           name: {type: String, default: ""},
+           steps: [String]
+         }],
+         images: [{
+           alt: String,
+           caption: String,
+         }],
+         translationStatus: {
+           type: String,
+           enum: ['pending', 'approved', 'needs_update'],
+           default: 'pending'
+         },
+         lastTranslated: {type: Date},
+         changedFields: [String],
+       }
+     },
+
+     // Translation metadata for tracking changes
+     translationMetadata: {
+       lastModifiedGerman: {type: Date},
+       fieldsModifiedSinceTranslation: [String],
+     },
      }, {timestamps: true}
 );
 
+// Indexes for efficient querying
+RecipeSchema.index({ "translations.en.short_name": 1 });
+
 export const Recipe = mongoose.model("Recipe", RecipeSchema);