chore: move dev dependencies to requirements-dev.txt

Separate production and dev dependencies. requirements.txt stays
lean for HF Spaces; requirements-dev.txt consolidates pytest, ruff,
ty, pdfplumber, and pycountry.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

requirements-dev.txt

@@ -1,2 +1,5 @@
 pdfplumber>=0.11,<1
 pycountry>=24,<25
+pytest>=8,<9
+ruff>=0.11,<1
+ty>=0.0.1a7

requirements.txt

@@ -1,4 +1,3 @@
-# App
 accelerate>=1,<2
 gradio>=5,<7
 sentencepiece>=0.2,<1
@@ -6,8 +5,3 @@ spaces>=0.34,<1
 tokenizers>=0.21,<1
 torch>=2,<3
 transformers>=4,<5
-
-# Dev
-pytest>=8,<9
-ruff>=0.11,<1
-ty>=0.0.1a7