Add experimental EFA support

Squashed commit of the following:

commit b7457791
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Sun Jun 15 08:18:46 2025 +0200

    changelog

commit 7f3d6106
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Sat Jun 14 19:55:51 2025 +0200

    Mark EFA backends as experimental for now

    For instance, VRR has very interesting issues when checking into departures
    that do not have real-time data yet.

commit 3370c0f6
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Sat Jun 14 19:49:48 2025 +0200

    InTransit: remove debug output

commit deb5444f
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Sat Jun 14 19:12:44 2025 +0200

    frontend js for checked-in view: never show fractional delays

commit d47ff961
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Sat Jun 14 19:12:31 2025 +0200

    worker: add EFA support

commit 3a955c01
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Sat Jun 14 17:48:46 2025 +0200

    EFA: checkin support

    worker support and cancellations are still missing

commit 19dea1ad
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Sat Jun 14 14:32:59 2025 +0200

    actions.js: pass on efa parameter

commit 8f18ff2c
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Sat Jun 14 14:32:48 2025 +0200

    EFA: implement geolocation lookup

commit bce1139b
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Sat Jun 14 14:32:21 2025 +0200

    EFA: ->id is no longer supported, use ->id_num

commit e4397e6b
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Mon Jun 9 20:34:22 2025 +0200

    ... derp

commit e0c4cbf8
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Mon Jun 9 18:28:35 2025 +0200

    database: it's dbris, not ris

commit bfb1e834
Merge: 42f9a00d f1da50f9
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Mon Jun 9 18:20:51 2025 +0200

    Merge branch 'main' into efa-support

commit 42f9a00d
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Wed Jan 8 18:11:28 2025 +0100

    EFA support (WiP)