refactor: restructure repository with separate backend and frontend directories

- Move Java backend to backend/ directory
- Create frontend/ directory for TypeScript TUI and future WebUI
- Update .gitignore for Node.js and worktrees
- Update README.md with new repository structure
- Copy documentation to backend/

docs/mvp/ddd/06-labeling-bc.md

@@ -1,42 +0,0 @@
-# Labeling BC - Detailliertes Domain Model
-
-**Bounded Context:** Labeling
-**Domain Type:** CORE
-**Verantwortung:** Automatische Berechnung von Nährwerten/Allergenen, Etikettengenerierung
-
-## Aggregates
-
-### ProductLabel (Aggregate Root)
-
-```
-ProductLabel
-├── ProductLabelId
-├── ArticleId - Reference to Master Data
-├── RecipeId - Reference to Production BC (for auto-calculation)
-├── ProductName
-├── Manufacturer
-├── Ingredients[] (Entity) - From Recipe, sorted descending by weight
-├── Allergens[] (VO) - Auto-calculated from ingredients
-├── TraceDeclarations[] (VO) - "May contain traces of..."
-├── NutritionFacts (Entity) - Auto-calculated from recipe
-│   ├── EnergyKJ, EnergyKcal, Fat, SaturatedFat, Carbs, Sugars, Protein, Salt
-│   └── CalculationBase (PER_100G | PER_PORTION)
-├── QualityLabels[] (VO) - Bio, Regional, Animal Welfare
-├── OriginLabeling (VO)
-└── LabelVersion
-
-Invariants:
-- All EU allergens must be declared
-- Ingredients sorted by quantity (highest first) - EU regulation
-- Nutrition facts must sum correctly from recipe
-- If BIO label, all ingredients must be BIO-certified
-- Allergens automatically inherited from ingredients (no manual override!)
-```
-
-## Use Cases
-
-```java
-GenerateLabelFromRecipe - Calculates nutrition & allergens from recipe
-PrintLabelAtScale - Sends label to scale for printing with current weight
-UpdateAllergenMatrix - Regenerates allergen matrix for all products
-```