Fix mssql-techempower Linux initialization for sqlcmd v18 and deterministic startup

[Copilot]

The SQL Server TechEmpower image was starting the engine but failing DB bootstrap because sqlcmd moved to mssql-tools18, leaving hello_world/world/fortune uninitialized. This updates startup/import behavior to be ODBC 18 compatible, readiness-driven, and fail-fast on init errors.

• Startup/import reliability

  • import-data.sh now uses /opt/mssql-tools18/bin/sqlcmd with ODBC 18 TLS option -C.
  • Replaced fixed sleep 20s with bounded readiness polling (SELECT 1) and explicit timeout failure.
  • Added -b so SQL execution errors return non-zero instead of continuing silently.

• Container failure semantics

  • entrypoint.sh now supervises sqlservr + import flow so initialization failure terminates container startup (non-zero) instead of leaving a running but uninitialized instance.

• TechEmpower dataset alignment

  • Updated create.sql world value generation from 0..9999 to canonical inclusive 1..10000.
  • Preserved required dataset shape: 10,000 world rows and 12 standard fortune rows.

• Tooling-path drift guard

  • Added a lightweight Dockerfile check for expected sqlcmd path presence (/opt/mssql-tools18/bin/sqlcmd) to catch base-image path regressions early.

# import-data.sh (core behavior)
sqlcmd_path="/opt/mssql-tools18/bin/sqlcmd"
sqlcmd=("$sqlcmd_path" -S localhost -U sa -P "$SA_PASSWORD" -C)

"${sqlcmd[@]}" -l 1 -Q "SELECT 1"   # readiness probe (retry/timeout loop)
"${sqlcmd[@]}" -b -d master -i create.sql

[sebastienros]

Can be updated later to a newer version