fix(historical): return error instead of panic on unknown timezone

[wboayue]

Summary

parse_time_zone in src/market_data/historical/common/decoders/mod.rs panicked when find_timezone returned no match. Both call sites already return Result<_, Error>, so propagate the failure as the typed Error::UnsupportedTimeZone(name.to_string()). Its display already carries the register_timezone_alias / IBAPI_TIMEZONE_ALIASES registration hint added in #465.

Why

After #465 added register_timezone_alias and IBAPI_TIMEZONE_ALIASES, users can extend the alias table at runtime. But parse_time_zone would still crash the whole process on an unmapped name in a historical schedule or bar response, defeating the registry escape hatch for the historical-data path. Now the failure is recoverable with the same fix pointers.

Test plan

• cargo +1.95.0 fmt
• cargo +1.95.0 clippy --all-targets -- -D warnings
• cargo +1.95.0 clippy --all-targets --features sync -- -D warnings
• cargo +1.95.0 clippy --all-features
• cargo +1.95.0 test --features sync (historical: 92 passed)
• cargo +1.95.0 test --features async (historical: 62 passed)
• New unit test test_decode_historical_schedule_unknown_timezone_errors exercises the error path, asserts the typed variant via matches!, and asserts the rendered message contains register_timezone_alias and IBAPI_TIMEZONE_ALIASES.

Companion PR

v2-stable port: #466.