[INFRA] Cleanup CI

[eseiler]

• Debian cron should build source package and use that
• rename ci_*.yml to cron_*.yml for crons
• crons shouldn't try to do seqan orga specific things when run on fork (api-stability, etc)

[seqan-actions]

Documentation preview available at https://docs.seqan.de/preview/seqan/seqan3/3338

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.11%. Comparing base (d660a79) to head (c93e8c0).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3338   +/-   ##
=======================================
  Coverage   98.11%   98.11%           
=======================================
  Files         270      270           
  Lines       11913    11913           
  Branches      104      104           
=======================================
  Hits        11688    11688           
  Misses        225      225           

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