Fix deptry: drop unused deps and mark dev group as dev-only

deptry (which scans only src/) reported five DEP002 findings:

- pytz and pyarrow were declared as runtime dependencies but are not
  imported anywhere in src/ or tests/. Removed them.
- pytest, pytest-cov and httpx are test-only tooling used under tests/,
  which deptry does not scan, so they were flagged as unused. Configured
  pep621_dev_dependency_groups = ["dev"] so deptry treats that optional
  group as dev dependencies.

Lockfile regenerated to drop pyarrow.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: tschm

pyproject.toml

@@ -25,8 +25,6 @@ dependencies = [
     "numpy>=1.26.0,<3.0.0",
     "pydantic>=2.7.0,<3.0.0",
     "uvicorn[standard]>=0.24.0,<1.0.0",
-    "pytz>=2024.1,<2026.0",
-    "pyarrow>=22.0.0,<23.0.0",
 ]
 
 [project.optional-dependencies]
@@ -36,6 +34,11 @@ dev = [
     "httpx>=0.27.0,<0.29.0",
 ]
 
+[tool.deptry]
+# The "dev" optional-dependency group holds test-only tooling that is used
+# under tests/ (which deptry does not scan), not in the src/ package.
+pep621_dev_dependency_groups = ["dev"]
+
 [project.urls]
 Homepage = "https://github.com/alihaskar/pycharting"
 Repository = "https://github.com/alihaskar/pycharting"