Resume Deep Scans after coordinator restarts

[ianw-oai]

Summary

• Resume an unfinished Deep Scan after its coordinator stops.
• Keep completed reviews and the original continuation token.
• Prevent an old coordinator from changing a recovered scan.
• Keep the existing setup page and public scan fixes.

Verification

• Runtime, recovery, and workbench tests: 136 passed; 7 Windows-only tests skipped.
• Coordinator restart and lease tests: 16 passed.
• Stopped the real scan server, resumed the same scan, and completed its report data.
• TypeScript, formatting, Python lint, and git diff --check passed.