Rename package to arca-models

[jcardozo-eth]

Summary

Renames all internal references from data-archive-models to arca-models to match the repo rename under the Arca umbrella.

• Rename schemas/data-archive/ → schemas/arca/
• Update Maven artifact, Java package (ch.ethz.library.arca.model), and GitHub Packages deploy URL in pom.xml
• Update ci/mvn_settings.xml repository URL
• Rename src/data_archive/ → src/arca_models/ and update pyproject.toml
• Regenerate uv.lock
• Update CI workflow name and paths
• Rename Java test package from darc to arca
• Update Python scripts and documentation

Consumer migration

Java

pom.xml — before:

<dependency>
    <groupId>ch.ethz.library</groupId>
    <artifactId>data-archive-models</artifactId>
</dependency>

After:

<dependency>
    <groupId>ch.ethz.library</groupId>
    <artifactId>arca-models</artifactId>
</dependency>

.java imports — before:

import ch.ethz.library.darc.model.*;

After:

import ch.ethz.library.arca.model.*;

Python

pyproject.toml / requirements.txt — before:

data-archive-models

After:

arca-models

.py imports — before:

from data_archive import ...

After:

from arca_models import ...

The old data-archive-models packages on GitHub Packages and TestPyPI will be deleted after this lands.