Complete INT04-A official backtest competitions

[hjcud]

Scope

Completes INT04-A (official BACKTEST competition) only. INT04-B LIVE_PAPER remains deferred and backend #278 must not be merged for this release.

What this adds

• operator-only official BACKTEST room creation that atomically locks 2+ hidden periods, official datasets, feature materializations, and one execution policy
• competition-period request creation after the evaluation ledger is durably opened
• scheduled settlement of terminal period runs into immutable aggregate results and PUBLISHED/FINAL leaderboards
• per-participant failure isolation for terminal runs and malformed result evidence
• BACKTEST-specific room cutoff handling: PENDING_LEDGER counts toward minimum participation and under-subscribed bots never start as private live bots
• batch runtime grants and executable-SQL regression coverage for every new write

Release dependencies

Do not request pointer/deploy until this PR and root #495 are merged and green.

The root pointer/deploy change must also refresh the Flyway bundle and extend the database bootstrap runtime-role checks for:

• competition.backtest_period_runs UPDATE
• competition.backtest_aggregate_results INSERT
• competition.leaderboard_snapshots INSERT
• competition.leaderboard_entries INSERT
• competition.room_final_access_grants INSERT

After deployment, read-only verify the real batch role privileges, backend-batch and backtest-worker image digests, Terraform/Flyway state, and queue wiring before running one fresh INT04-A journey. Preserve all existing runs and DLQs; do not receive, delete, or redrive them.

Verification

• gradlew test --no-daemon --build-cache --parallel (passed, 9m55s before rebase)
• gradlew test :apps:idea2strategy-cli:distZip --no-daemon --build-cache --parallel (passed, 9m46s on final develop/Automatically select official backtest inputs #279 combination)
• scripts/test-container-contracts.sh via Git Bash (passed)
• targeted PostgreSQL integration coverage for room creation, evaluation scheduling cutoff, settlement, result isolation, leaderboard publication/finalization, idempotence, and invalid evidence isolation
• DatabaseAccessPolicyTest and RoleGrantsCoverExecutedSqlTest (passed)

Final recording after AWS proof must remain: INT04-A 자동 백테스트 대회 완료 / INT04-B 라이브 평가 보류.