Pin major versions in requirements.txt

Constrain all dependencies to major version ranges to prevent
unexpected breaking changes from upstream releases.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

requirements.txt

@@ -1,6 +1,13 @@
-accelerate
-sentencepiece
-tokenizers
-torch
-transformers
-gradio
+# App
+accelerate>=1,<2
+gradio>=5,<6
+sentencepiece>=0.2,<1
+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