Extract Cooklang types into Data.CookLang module

- Create src/Data/CookLang.hs with all recipe types (Recipe, Section,
  StepItem, Ingredient, Cookware, Timer, RecipeRef, Quantity, Duration,
  Metadata, emptyMetadata)
- Data.CookLang has zero Roux imports — can be extracted to its own
  package
- Roux.Types now just re-exports from Data.CookLang
- Update all Roux.* modules and tests to import Data.CookLang directly
- All 30 tests passing, hlint clean

test/Roux/ParserSpec.hs

@@ -7,7 +7,7 @@ import qualified Data.Text.IO as TIO
 import Test.Hspec (Spec, describe, expectationFailure, it, shouldBe)
 
 import Roux.Parser (parseCookFile)
-import Roux.Types
+import Data.CookLang
 
 spec :: Spec
 spec = do