Define Cooklang data model and add DerivingStrategies + containers deps

- Add full Cooklang (.cook) recipe data model to Roux.Types:
  Recipe, Section, Step, StepItem (with StepText/StepIngredient/
  StepCookware/StepTimer/StepRecipeRef/StepNote/StepComment/StepBreak),
  Ingredient, Cookware, Timer, RecipeRef, Quantity, Duration, Metadata
- Enable DerivingStrategies extension project-wide
- Add containers to build dependencies

package.yaml

@@ -9,6 +9,7 @@ copyright:   2026 James Brechtel
 license:     BSD-3-Clause
 
 default-extensions:
+  - DerivingStrategies
   - OverloadedStrings
 
 ghc-options:
@@ -28,6 +29,7 @@ dependencies:
   - blaze-html
   - blaze-markup
   - bytestring
+  - containers
   - directory
   - http-types
   - optparse-applicative