chore: migrate build system from setuptools to hatchling

- Replace setup.cfg with pyproject.toml using hatchling build backend
- Switch from requests to httpx + pydantic v2 dependencies
- Add uv.lock for deterministic dependency resolution
- Add pytest + ruff dev dependencies with configurations
- Update .gitignore for .ruff_cache/
- Bump LICENSE year to 2026

.gitignore

@@ -156,6 +156,9 @@ dmypy.json
 # Cython debug symbols
 cython_debug/
 
+# Ruff
+.ruff_cache/
+
 # PyCharm
 #  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
 #  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore