Add (possibly still somewhat experimental) MOTIS support

Squashed commit of the following:

commit c7c8b2ec
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Mon Jun 9 13:08:57 2025 +0200

    fix another merge issue

commit d2ae55c9
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Mon Jun 9 13:08:39 2025 +0200

    Stations: get_by_external_id is a slow function

commit 72517441
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Mon Jun 9 13:05:48 2025 +0200

    ... I accidentally commited a merge conflict

commit c695494d
Merge: e5da62bc 3322ca23
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Mon Jun 9 12:46:08 2025 +0200

    Merge branch 'main' into motis

commit e5da62bc
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Wed Apr 30 18:15:39 2025 +0200

    cpanfile: add Travel::Status::MOTIS dependency

commit 180723a9
Merge: 479373b1 c90ae4cf
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Wed Apr 30 18:13:45 2025 +0200

    Merge branch 'main' into motis

commit 479373b1
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Wed Apr 30 18:06:41 2025 +0200

    database: remove duplicate users_with_backend migration

commit 94c8b5a7
Author: Birte Kristina Friesel <derf@finalrewind.org>
Date:   Wed Apr 30 18:06:04 2025 +0200

    Do not store train colours in database. They're only supported by MOTIS.

commit d58f23c3
Author: networkException <git@nwex.de>
Date:   Fri Apr 18 11:47:02 2025 +0200

    Initial MOTIS backend support

    This patch adds support for checkins using MOTIS backends
    using the Travel::Status::MOTIS module.

    With this travelynx supports the two services currently
    exposed by the module, RNV for local transit in Mannheim,
    Germany and surrounding cities and transitous for worldwide
    crowdsourced tranit feeds.

    This implementation supports realtime predictions,
    cancellations and polylines as well as custom route colors
    if available.

    As MOTIS doesn't expose names of indivial trips currently,
    displaying transports is mostly limited to route names.

    MOTIS uses strings for stop ids, based on the used GTFS
    source feeds. As travelynx's data model currently assumes
    interger station ids, this patch adds a mapping table
    to the database.

    This patch assumes support for MOTIS in db-fakedisplay.

    Note that while träwelling has migrated to tranitous fully
    sync remains unsupported for now.

    See https://github.com/Traewelling/traewelling/issues/3345