setup documentation: update dependencies and update workflow

## Dependencies

 * perl ≥ 5.20

 * carton

 * build-essential

 * libpq-dev

On Debian 13 (trixie), the following packages are required:

 * perl ≥ 5.40

 * carton (Perl package manager)

 * build-essential (C/C++ compiler and build utilities)

 * git

 * libdb5.3-dev

 * libpq-dev

 * libssl-dev

 * libxml2-dev

 * zlib1g-dev

## Installation

travelynx depends on a set of Perl modules which are documented in `cpanfile`.

After installing the dependencies mentioned above, you can use carton to

After installing the dependencies mentioned above, you can use **carton** to

install Perl depenencies locally. You may alsobe able to use cpanminus;

however this method is untested.

however, this method is untested.

In the project root directory (where `cpanfile` resides), run

carton install --deployment

```

and set `PERL5LIB=.../local/lib/perl5` before executing any travelynx

commands (see configs in the examples directory) or wrap them with `carton

exec`, e.g. `carton exec hypnotoad index.pl`

Afterwards, either set `PERL5LIB=.../local/lib/perl5` before executing any

travelynx commands (see configs in the examples directory), or wrap them with

`carton exec`, e.g. `carton exec hypnotoad index.pl`

## Setup

## Updating

It is recommended to run travelynx directly from the git repository. When

updating, the workflow depends on whether schema updates need to be applied

or not.

```

git pull

carton install --deployment # if you are using carton: update dependencies

chmod -R a+rX . # only needed if travelynx is running under a different user

if perl index.pl database has-current-schema; then

    systemctl reload travelynx

else

    systemctl stop travelynx

    perl index.pl database migrate

    systemctl start travelynx

fi

```

It is recommended to run travelynx directly from the git repository.  This way,

**examples/update.sh** will automatically perform a git pull and apply any

required database migrations. For releases that bump dependency versions or

introduce new dependencies, run **examples/update.sh with-deps**.

Note that this is subject to change -- the application may perform schema

updates automatically in the future. If you used carton for installation,

use `carton exec perl ...` in the snippet above; otherwise, export

`PERL5LIB=.../local/lib/perl5`.

If you are not using carton, or have some other peculiarities in your setup,

you may need to adjust the script.

## Setup with Docker

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