Add full regression mode to integration test runner

[JayVDZ]

Summary

Add an -Scenario All option to Run-IntegrationTests.ps1 that runs every implemented integration test scenario in sequence, performing lightweight resets between scenarios. This enables a full regression test in a single invocation without redundant build or infrastructure startup steps.

Problem

Each integration test scenario must currently be run individually. Running a full regression suite requires manually invoking the script multiple times, each time paying the cost of Docker image builds, Samba AD startup, and service health checks. For 6 implemented scenarios, this means ~15-20 minutes of redundant infrastructure overhead.

Proposed Approach

1. Build once — Docker images built at the start and reused
2. Start all external systems upfront — All Samba AD instances started once
3. Lightweight reset between scenarios — Reset JIM database and clean Samba AD OUs without rebuilding containers
4. Aggregated results — Combined pass/fail summary with per-scenario breakdown
5. Continue on failure — A failing scenario doesn't abort the remaining tests

Plan Document

See docs/plans/INTEGRATION_TEST_FULL_REGRESSION.md for the full design including infrastructure grouping, reset strategy, results format, and implementation notes.

Scope

• Modify test/integration/Run-IntegrationTests.ps1 to support -Scenario All
• Add "All Scenarios" to the interactive scenario menu
• Implement lightweight reset function between scenarios
• Aggregate results into a single JSON output

Acceptance Criteria

• ./Run-IntegrationTests.ps1 -Scenario All -Template Nano runs all implemented scenarios sequentially
• Interactive menu includes "All Scenarios (full regression)" option
• JIM database is fully reset between scenarios (clean state)
• Samba AD test data is cleaned between scenarios
• Docker images are only built once at the start
• External system containers are only started once
• A failing scenario does not prevent subsequent scenarios from running
• Aggregated results JSON saved to test/integration/results/
• Exit code is non-zero if any scenario failed