docs: update TPCC benchmark results

[KKould]

Summary

• Update the root README TPCC comparison table with the latest full 720s matrix run.
• Update tpcc/README.md with the same 720s summary plus refreshed raw outputs for KiteSQL LMDB, KiteSQL RocksDB, SQLite balanced, and SQLite practical.

TPCC Results

Run: ./scripts/run_tpcc_matrix.sh with default TPCC duration, --num-ware 1, default --max-retry 5.

Backend	TpmC	New-Order p90	Payment p90	Order-Status p90	Delivery p90	Stock-Level p90
KiteSQL LMDB	73638	0.001s	0.001s	0.001s	0.002s	0.001s
KiteSQL RocksDB	39051	0.001s	0.001s	0.002s	0.009s	0.001s
SQLite balanced	39835	0.001s	0.001s	0.001s	0.001s	0.001s
SQLite practical	37911	0.001s	0.001s	0.001s	0.001s	0.001s

All variants completed successfully and passed TPCC constraint checks.

Test

• git diff --check origin/main...HEAD