Add colored severity badges to terminal scan output

[KryptosAI]

Summary

Add colored severity badges (PASS/FAIL/WARN) to terminal scan output, replacing or supplementing the current plain-text status indicators.

Files to modify

• src/reporters/terminal.ts

What to change

1. Import chalk (already a project dependency) for colored output.
2. In the terminal reporter's result rendering, wrap severity labels in colored badges:
   • PASS → green background badge: chalk.bgGreen.black(' PASS ')
   • FAIL → red background badge: chalk.bgRed.white(' FAIL ')
   • WARN → yellow background badge: chalk.bgYellow.black(' WARN ')
3. Apply the same styling to the per-check result lines and the overall score line.
4. Ensure badges are still legible when --accessible is set (fall back to text-only labels as in Replace Unicode symbols with [PASS]/[FAIL]/[WARN] text labels in terminal reporter when --accessible is set #233).

Expected behavior

Terminal output after mcp-observatory test shows green PASS, red FAIL, and yellow WARN badges for each check result.

Estimated time

~15 minutes

[albatrossflyon-coder]

Hi! I'd like to work on this one.