refactor: replace aeson ToJSON/FromJSON with json-fleece schemas

- RecipeSearchEntry: replace genericToJSON ToJSON with Fleece schema
  using object combinators (required, optionalNullable, list text)
- SchemaOrgRecipe: replace manual FromJSON instance with Fleece decoder
  that reuses existing helper functions for quirky fields
- Html.hs: use Fleece.Aeson.Encoder.encode instead of Data.Aeson.encode
- stack.yaml: add shrubbery + json-fleece extra-deps
- package.yaml: add json-fleece-aeson + json-fleece-core deps
- Remove unused LANGUAGE pragmas and redundant brackets

roux-server.cabal

@@ -47,6 +47,8 @@ library
     , directory
     , filepath
     , http-types
+    , json-fleece-aeson
+    , json-fleece-core
     , optparse-applicative
     , parsec
     , text
@@ -79,6 +81,8 @@ executable check-recipes
     , directory
     , filepath
     , http-types
+    , json-fleece-aeson
+    , json-fleece-core
     , optparse-applicative
     , parsec
     , roux-server
@@ -112,6 +116,8 @@ executable roux-server
     , directory
     , filepath
     , http-types
+    , json-fleece-aeson
+    , json-fleece-core
     , optparse-applicative
     , parsec
     , roux-server
@@ -151,6 +157,8 @@ test-suite roux-server-test
     , filepath
     , hspec
     , http-types
+    , json-fleece-aeson
+    , json-fleece-core
     , optparse-applicative
     , parsec
     , roux-server