fix: use OS trust store for TLS verification via truststore

Regression from #62: verify_ssl true used to resolve to the system CA
bundle path, so corporate CAs installed in the OS worked; after the
unification true became requests' default (certifi), breaking setups
with a corporate CA in the system store.

Now verify_ssl true injects truststore, so requests verifies against
the OS trust store on any platform. verify_ssl false / custom CA path
behavior is unchanged. Tests mock truststore via an autouse fixture to
keep the pytest process free of global ssl mutation.

Refs #62

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "redmine-reporter"
-version = "1.11.0"
+version = "1.11.1"
 description = "Redmine time-entry based issue reporter for internal use"
 readme = "README.md"
 authors = [{ name = "Artem Kokos", email = "artem-kokos@mail.ru" }]
@@ -25,6 +25,7 @@ dependencies = [
     "openpyxl>=3.1.0",
     "pyyaml>=6.0",
     "requests>=2.31",
+    "truststore>=0.10",
     "urllib3>=1.26",
 ]