Contribute: GTFS sensor optimizations

[renemarc]

As a developer, I want to publish my GTFS component improvements so that other users can benefit from them.

Acceptance criteria

1. It's done when a Home Assistant PR is submitted to support for next departures.
2. It's done when a Home Assistant PR is submitted to document database speed-up tweaks.

References

• /gtfs/README.md
• https://community.home-assistant.io/t/faster-gtfs-schedule-lookups/37624

[renemarc]

Currently creating a series of GTFS pull requests to cover the following:

• Clarify SQL query
• Set icon per route type
• Adjust arrival date to tomorrow when bus arrives after midnight
• Extend lookup to include departures crossing midnight
• Search tomorrow when no more departures today (optional)
• Return None instead of "0 minutes" when no more departures
• Cache metadata queries
• Enable departure, timer, countdown, and auto state modes
• Fix default name handling to prevent entity_id changes
• Support multiple departures/sensors (with internal cache)
• Adding missing indexes to SQLite database
• Prevent race conditions when building the database
• Add type hints + Code cleanup