Add minimal Cooklang parser with first tests

- Create Roux.Parser with parseCookFile (splits paragraphs, treats
  each as a plain-text step, no metadata parsing yet)
- Add emptyMetadata to Roux.Types for convenience
- Add test dependencies: hspec, tasty-golden, tasty-hspec
- Add ParserSpec with 4 tests covering single step, multiple steps,
  empty input, and whitespace trimming
- Wire ParserSpec into test runner via tasty-hspec

roux-server.cabal

@@ -17,6 +17,7 @@ build-type:     Simple
 library
   exposed-modules:
       Roux
+      Roux.Parser
       Roux.Types
   other-modules:
       Paths_roux_server
@@ -78,6 +79,7 @@ test-suite roux-server-test
   type: exitcode-stdio-1.0
   main-is: Spec.hs
   other-modules:
+      Roux.ParserSpec
       Paths_roux_server
   autogen-modules:
       Paths_roux_server
@@ -94,11 +96,14 @@ test-suite roux-server-test
     , bytestring
     , containers
     , directory
+    , hspec
     , http-types
     , optparse-applicative
     , parsec
     , roux-server
     , tasty
+    , tasty-golden
+    , tasty-hspec
     , tasty-hunit
     , text
     , time