feat: implement PLEXOS solution reader and setup master files for 9-12 versions

[mcllerena]

No description provided.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.64234% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.98%. Comparing base (2fc5da5) to head (3f58de3).

Files with missing lines	Patch %	Lines
src/plexosdb/db.py	86.53%	14 Missing ⚠️
src/plexosdb/solution_reader.py	98.44%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
+ Coverage   95.55%   95.98%   +0.43%     
==========================================
  Files           8        9       +1     
  Lines        1823     2468     +645     
==========================================
+ Hits         1742     2369     +627     
- Misses         81       99      +18     

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[mcllerena]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Merge conflicts have been resolved in commit 0c97e00.

The key resolutions were:

• db.py: Fixed PROPERTY_QUERY path to use plexosdb.sql (correct), merged create_schema to support both versioned master template loading (int/tuple/v-string) from this PR and config-only string version updates + seed_defaults from main, added _seed_default_model_data from main
• docs/source/howtos/create_db.md and docs/source/tutorial.md: Combined documentation from both branches covering all features

All 892 tests pass.