Add scan budget controls

[AmirrezaFarnamTaheri]

Summary

• add scan worker budget presets for quick, balanced, deep, expert, high, and max scan runs up to 128 workers
• keep the worker slider available for custom values while clamping UI, persisted settings, and service launch requests to the shared scan limit
• update scan guidance so higher budgets clearly communicate battery, heat, CPU, and upload tradeoffs

Notes

• The default remains conservative; higher budgets are opt-in from the Scan tab.
• This changes scanner worker budget controls only and does not change StormDNS internals.

Verification

• git diff --check
• conflict-marker search across tracked source files

[AmirrezaFarnamTaheri]

Closing this smaller branch to keep the active upstream queue non-overlapping. Its scan-budget direction will be handled in a later resolver-testing batch after the setup/profile and structured-result PRs are settled.