Performance enhancements, time indices and secondary indices for Convex-db

[trsb-standards]

Added various performance improvements for disk space usage of etch and memory usage of the Convex-DB

Added:

• secondary indices API
• versioned tables and time indices

[mikera]

(Claude Comment) Thanks @trsb-standards — there is clearly valuable work in here, but at +8,250 lines across 40 files it is too large to review and merge in one go. We would like to take it, broken into atomic, independently verifiable and mergeable steps.

The natural split seems to be the three features named in the description, each as its own PR with its own tests:

1. Etch disk-usage / memory improvements — likely the most self-contained and easiest to land first
2. Secondary indices API
3. Versioned tables and time indices (building on 2 if there is a dependency)

Encouragingly, the branch currently merges clean against develop (no textual conflicts despite the April base), so now is a good moment to do the split rather than letting it drift. Smaller PRs will also get CI runs and review turnaround in days rather than months. Happy to review the first slice as soon as it is up.