feat(enterprise): recover interrupted analysis runs

[Gracker]

Summary

• Add startup recovery for enterprise analysis_runs: pending/running/awaiting_user rows left by a previous backend process are marked failed with backend_startup_recovery error metadata.
• Invoke the recovery path during backend bootstrap only when enterprise mode is enabled.
• Extend restart persistence tests so terminal runs stay completed while interrupted running runs become failed.

Scope notes

• Advances README §11.11 / D9: backend restart now leaves analysis run state explicit instead of indefinitely running.
• This does not close README §0.4.12; the full §11.11 checklist and final design-audit evidence are still incomplete.
• README TODO state is unchanged.

Validation

• cd backend && PATH="$HOME/.nvm/versions/node/v24.15.0/bin:$PATH" npx jest --runInBand --forceExit src/services/__tests__/analysisRunStore.test.ts src/routes/__tests__/enterpriseRestartPersistence.test.ts
• cd backend && PATH="$HOME/.nvm/versions/node/v24.15.0/bin:$PATH" npm run typecheck
• PATH="$HOME/.nvm/versions/node/v24.15.0/bin:$PATH" npm run verify:pr