v0.3.0

A small release with a behavior change to "not found" handling and more predictable defaults.

404s on single-ticker lookups now return None

get_ticker_overview and get_ticker_events (and their _raw variants) now return None when the
ticker doesn't exist (HTTP 404) instead of raising:

overview = await api.reference_api.get_ticker_overview("NOPE")
if overview is None:
    ...  # unknown ticker

This is a behavior change: those methods now return Optional, so a None check is required.
Other errors (401, 429, 5xx) still raise as before, and list endpoints like get_all_tickers
continue to return an empty list.

Defaults are now set client-side

sort, order, and active now default explicitly in the client (e.g. tickers sort by ticker
ascending, splits by execution_date descending) instead of relying on the API's defaults. This
makes results deterministic and independent of any server-side changes.