fix(audit): stop re-billing Lighthouse on workflow and parse retries

[Ayush7614]

Summary

• Site-audit Lighthouse batches used default Cloudflare Workflow retries (limit 5). A mid-batch failure after DataForSEO already charged (e.g. R2/D1 write) re-ran the whole batch and billed again.
• Post-assertOk Lighthouse parse failures threw plain Error, so Autumn metering skipped the spend and in-process retries called DataForSEO again.
• Aligns metered Lighthouse steps with rank-check’s single-attempt pattern, meters charged parse failures, and soft-fails instead of retrying billed errors.

How to review

1. siteAuditWorkflowPhases.ts — LIGHTHOUSE_BATCH_STEP_CONFIG with retries.limit: 0
2. dataforseo/lighthouse.ts — billing built before parse; parse failures become DataforseoChargedTaskError
3. audit/lighthouse.ts — break the 3-attempt loop on charged errors
4. Unit test covers the parse-after-bill path

Test plan

• pnpm exec vitest run src/server/lib/dataforseo/lighthouse.test.ts src/server/lib/audit/lighthouse.test.ts
• Spot-check a hosted site audit Lighthouse batch failure does not re-fetch already-charged URLs