fix(bootstrap): increase namespace wait timeout to ~180s

[riyadhctg]

Summary

Increases the wait_for_namespace() timeout from ~120s to ~180s to prevent
bootstrap failures on first run when K3s needs extra time to pull images and
initialize.

Related Issue

Fixes part of #143

Changes

• Increase attempts from 60 to 90 in wait_for_namespace()
  (crates/openshell-bootstrap/src/lib.rs)

Testing

• mise run pre-commit passes
• Unit tests added/updated
• E2E tests added/updated (if applicable)
• Manual testing: verified gateway starts successfully on Colima (4 CPU, 8GB
  RAM) where it previously timed out

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (if applicable)

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[riyadhctg]

I have read the DCO document and I hereby sign the DCO.