chore(jobsdb): add consumer columns

[atzoum]

Summary

Adds two new columns to all jobsdb tables (jobs and job_status) as the foundational schema step for multi-consumer jobsdb support:

• consumers on jobs tables — tracks which consumers a job is intended for
• consumer on job_status tables — identifies which consumer a status row belongs to

Both columns are added universally to all handles (single- and multi-consumer alike), with safe defaults that preserve existing single-consumer semantics. All existing read, write, and compaction paths are updated to carry the new columns through.

Linear Ticket

Resolves PIPE-3115

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

---

This is part 2 of 3 in a stack made with GitButler:

•  3  feat(jobsdb): multiconsumer datasets and flip #7083
•  2  chore(jobsdb): add consumer columns #7082 👈
•  1  feat(jobsdb): introduce compaction min ds age #7077

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.90%. Comparing base (dfef1f1) to head (f0c14c3).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7082      +/-   ##
==========================================
+ Coverage   79.49%   79.90%   +0.40%     
==========================================
  Files         583      583              
  Lines       65202    65207       +5     
==========================================
+ Hits        51835    52103     +268     
+ Misses      10295    10014     -281     
- Partials     3072     3090      +18     

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