feat: implement initial missing functions on main db

[mcllerena]

No description provided.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 73.10924% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.46%. Comparing base (fd605d0) to head (11cea1f).

Files with missing lines	Patch %	Lines
src/plexosdb/db.py	72.88%	32 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #170      +/-   ##
==========================================
- Coverage   96.22%   95.46%   -0.76%     
==========================================
  Files          20       20              
  Lines        3151     3244      +93     
==========================================
+ Hits         3032     3097      +65     
- Misses        119      147      +28     

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[pesap]

Please address the inline findings before merging. The update implementation should reuse the existing property validation and membership-resolution paths, and follow the established bulk insertion pattern for batch execution. Keep update_property() as a thin public wrapper; removing the shared helper is not required if it cleanly centralizes the selector logic. Please also add coverage for rollback after domain-validation failures, scenario-scoped updates, explicit parent membership selection, and reusing the connection after a failed batch.