fix: preserve crashlytics options

[IzaakGough]

Fixes #265

Summary

Alert-based function decorators were reconstructing FirebaseAlertOptions with only alert_type and app_id, which dropped shared handler settings like region, max_instances, retry, and secrets. This change preserves the full option set when building alert endpoints and adds coverage across the alert wrappers that delegate to FirebaseAlertOptions.

Problem/Root Cause

Issue #265 reports that Crashlytics alert handlers ignored configuration such as region, max instances, and secrets. The same pattern also applied to the other alert-specific option wrappers. In each _endpoint() implementation, the wrapper created a fresh FirebaseAlertOptions with just the alert identifiers, so the inherited EventHandlerOptions fields on the original options object never made it into the generated endpoint manifest.

Solution/Changes

Add a shared helper that copies the dataclass fields from the original alert options object into a new FirebaseAlertOptions, while overriding only alert_type and app_id where needed. Update the App Distribution, Crashlytics, Performance, and Billing option wrappers to use that helper before generating the endpoint. Expand tests/test_options.py with endpoint assertions that verify shared options are preserved for each alert wrapper and for direct alerts_fn.on_alert_published(...) usage.

Testing

• uv run pytest tests/test_options.py

[gemini-code-assist]

Code Review

This pull request introduces a helper function _alert_options_to_firebase_alert_options to streamline the conversion of event handler options to Firebase alert options, refactoring several _endpoint methods to use it, and adds comprehensive unit tests to verify option preservation. The reviewer suggested simplifying the helper function's signature by dynamically extracting app_id from the options object using getattr, which would eliminate the need to explicitly pass self.app_id in multiple _endpoint implementations.

[cabljac]

lgtm - i think Gemini comments are mostly cleanup nits, probably worth doing