fix(file): lazy load browse roots

[piorpua]

Summary

• Lazy-load shallow file browse roots instead of resolving them during backend startup.
• Add module-state phase logs so startup hangs point to the last incomplete phase.
• Cover lazy browse-root resolution with a unit test.

Verification

• Local dev startup succeeded; backend reached health checks and /api/fs/browse returned 200.
• just push
  • cargo fix --allow-dirty --allow-staged
  • cargo clippy --fix --workspace --allow-dirty --allow-staged -- -D warnings
  • cargo fmt --all
  • cargo nextest run --workspace: 5911 passed, 18 skipped