First Spicule release of mondrian with Calcite SQL backend

Highlights:
- Calcite SQL generation path (default -Dmondrian.backend=calcite)
- Automatic aggregate-table matcher — ~10x on matching queries without UseAggregates flip
- HSQLDB 4.8x faster, Postgres parity (geomean D/B = 1.01x)
- Jakarta servlet 6 migration (from javax.servlet)

See README.md for flags and docs/reports/perf-analysis-2026-04-22-postmerge.md for benchmarks.