fix: resolve ZoneInfo error by using IANA-compliant local timezone

Replaced local timezone detection using tzinfo string (e.g. "CEST")
with tzlocal.get_localzone_name() to ensure a valid IANA time zone
(e.g. "Europe/Paris") is passed to ZoneInfo. This avoids runtime
errors on macOS and other systems that return non-IANA tz abbreviations.

src/time/pyproject.toml

@@ -20,6 +20,7 @@ dependencies = [
     "mcp>=1.0.0",
     "pydantic>=2.0.0",
     "tzdata>=2024.2",
+    "tzlocal>=5.3.1"
 ]
 
 [project.scripts]