Add container image documentation and generic Slurm/HTCondor submission scripts

[afroch]

Summary

This pull request introduces the following changes

• Document the CI-built container image (upp:latest / upp:<tag>) in the setup docs, with apptainer and docker usage, including the CVMFS-unpacked path on unpacked.cern.ch
• Add a "Running on HPC" docs page covering interactive and batch usage of the container image on Slurm and HTCondor
• Ship generic batch submission scripts (scripts/batch/) that submit one job per component/region/split, deriving the job list from the preprocessing config; the scheduler (Slurm or HTCondor) is auto-detected
• Default to the CVMFS-unpacked image when available, falling back to the registry
• Add a list_components console script that enumerates the components defined in a config
• Document how to obtain the scripts without a local clone (copied from the image itself)

Conformity

• Changelog entry
• Documentation

[github-actions]

Docs preview: https://umami-hep.github.io/umami-preprocessing/pr-160/

[codecov]

Codecov Report

❌ Patch coverage is 95.45455% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.34%. Comparing base (281e9ab) to head (e905f2f).

Files with missing lines	Patch %	Lines
upp/utils/list_components.py	95.45%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #160   +/-   ##
=======================================
  Coverage   95.34%   95.34%           
=======================================
  Files          24       25    +1     
  Lines        2318     2340   +22     
=======================================
+ Hits         2210     2231   +21     
- Misses        108      109    +1     

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