Harden report rerun reset behavior in API v2 alpha

[anth-volk]

Fixes #229

Summary

• clear persisted simulation result state during report rerun by resetting household_result, output_dataset_id, and started_at
• keep rerun returning reports and simulations to a clean pending state
• add focused rerun coverage for both household and economy analyses, including result-row deletion and correct trigger-path assertions

Testing

• cd /tmp/policyengine-api-v2-alpha-enable-report-rerun && uv run pytest tests/test_analysis_rerun.py

Notes

• this hardens the existing POST /analysis/rerun/{report_id} route rather than introducing a new endpoint

[anth-volk]

Superseded by the report-output run migration plan. Closing in favor of the staged run-table redesign.