Validate graph, set-system, and database deserialization

[isPANN]

Summary

• Reuse constructor validation when loading five graph topologies, seven set-system models, and five database/query models.
• Normalize persisted inputs through the same construction path and remove duplicated create checks.
• Reject invalid attribute indices, relation arities, query arguments, and database frequency-table inputs during JSON loading.
• Preserve public constructors, solver and reduction interfaces, JSON field names, and existing planar edge-bound semantics (not a new planarity algorithm).
• Scope: 35 files, 936 additions; based on main.

Verification

• Workspace all-feature unit and integration tests: 6,495 passed, 2 ignored.
• Changed-line coverage against main: 100% (656 instrumented lines).
• Workspace all-target all-feature Clippy, formatting, and whitespace checks pass.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.97%. Comparing base (7dd5fcd) to head (dc4a670).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1161      +/-   ##
==========================================
+ Coverage   95.93%   95.97%   +0.04%     
==========================================
  Files        1074     1074              
  Lines      132106   132470     +364     
==========================================
+ Hits       126730   127144     +414     
+ Misses       5376     5326      -50     

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[GiggleLiu]

Follow-up items (recorded during final review, applies to the whole validation series #1161/#1162/#1164/#1166/#1168/#1169):

• The new fn try_new constructors are private. Some models already expose pub fn try_new (e.g. SetSplitting, ThreePartition), and reductions use it to propagate target-construction errors instead of panicking. Consider making the new ones pub with a doc comment so downstream code and reductions can construct these types fallibly.
• New tests use mixed naming (json_rejects_invalid_instance, deserialize_checks_the_edge_bound, ...). The repo convention is a test_ prefix.

[GiggleLiu]

Final review: every rejection traced to an existing assert; JSON shapes preserved; make check passes locally on the merged state. Approving as-is; follow-up note posted.