Add incremental pair-oracle maintenance

[gaperez64]

Summary

• add fixed-point incremental pair-oracle maintenance and public record-source APIs
• expose atomic sync.update_cells updates with lazy witness reads, epoch-scoped cache records, and bounded full-rebuild fallback
• add differential, Memgraph integration, and ablation tests plus CI coverage and end-user documentation
• document cached, uncached, and incremental workflows with a worked example and Mermaid lifecycle diagrams

Validation

• Clang builds and LLVM clang-format/clang-tidy checks
• ASan/UBSan unit tests
• Valgrind unit tests with zero errors and zero leaks
• local Memgraph integration and ablation suites
• 83.4% line coverage, above the 75% CI gate
• Memgraph 3.1 and 3.11 module-header compatibility