[1425] Backend: Audit cache invalidation across modules

[franklin251861-killer]

Summary

• Centralize cache keys, TTLs, generations, invalidation, discovery, and telemetry across backend modules.
• Fix confirmed write-to-dependent-cache gaps and add conservative invalidation for derived and operational read models.
• Replace unsafe transient error caching, make warm-cache and Soroban caches race-safe and bounded, and document the full inventory.
• Add consistency, invalidation, race, discovery, and metrics coverage.

Validation

• npm run build
• npx tsc --noEmit -p tsconfig.build.json
• npx tsc --noEmit -p tsconfig.test.json
• npm run migration:check
• Changed-file ESLint and Prettier checks
• git diff --check
• Full Jest suite: 94 passed, 1 skipped; 780 passed, 19 skipped; 2 snapshots passed

Closes #1425

[drips-wave]

@franklin251861-killer Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[Cedarich]

@franklin251861-killer Kindly resolve conflicts