feat: add unknown aircraft mapping to imports

[achatman]

Fixes #630. Also lays groundwork for fixing #664.

This is a rough draft, submitting for review on the approach.

These issues could be fixed by more intelligently mapping aircraft names, but that seems dangerous to me. Instead, I matched the existing approach for airlines and airports to let the user map the incoming values:

If you're interested in this approach, I can continue working on it. Or feel free to take it over.
Outstanding issues:

1. UI is not handling longer aircraft names well
2. If you map some of the values then import, the status bar gets out of sync (I believe this is preexisting):

3. I don't like how I handled the typing in import/index.ts with withDefaultUnknownValues. That was a quick workaround to get something testable
4. This only handles OpenFlights. I figured that's a good starting place for now, but it's worth reviewing other imports to see which could benefit from the same feature. Clearly Flighty can, but having no Apple devices, I can't find a way to create an import file for testing :(. Supporting other sources might also be better left for separate MRs, to keep things focused.
5. Unit tests
6. Support for creating a new Aircraft during the workflow
7. Oops, forgot prettier

Note

Add unknown aircraft mapping to Flighty and OpenFlights imports

• The import pipeline now detects unresolved aircraft during Flighty and OpenFlights imports, reports them as unknownAircraft in the result, and excludes affected flights from insertion until resolved.
• A new aircraft mapping UI in StatusStep.svelte lets users pick or create aircraft for unknown entries, mirroring the existing airport/airline mapping flow.
• AircraftPicker.svelte gains an onCreateNew callback that shows a "Create a new aircraft?" action when no search results are found.
• Applied airport, airline, and aircraft mappings are now accumulated across reprocess attempts and only cleared on reset.
• Behavioral Change: flights with unresolved aircraft are silently excluded from the inserted batch rather than inserted with a null aircraft reference.

^{Macroscope summarized a7ce499.}

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[johanohly]

Thank you for your contribution!