[Feature/optional] split managed service blocks into read-only section and improve editor behavior

[hololee]

Background

This PR simplifies the Dockerfile editing UX in Provisioning by separating managed service blocks (Jupyter/code-server)
from the user-editable Dockerfile area, improving clarity and reliability.

What Changed

• Dockerfile editor now shows and edits only user-authored content.
• Managed service blocks are rendered in a separate read-only section below the editor.
• Managed block section is now editor-like:
  • line numbers
  • Dockerfile syntax highlighting
• Fixed an issue where managed blocks did not reappear after unchecking and rechecking service toggles:
  • enabled Monaco automaticLayout
  • added min-h-0 to the main editor container
• Template save/load flow simplified:
  • save user Dockerfile only
  • load user Dockerfile only
• Fixed i18n gap:
  • removed hardcoded "Managed Service Blocks"
  • added provisioning.managedServiceBlocks key to both en and ko

Scope

• frontend/src/pages/Provisioning.tsx
• frontend/src/i18n/locales/en/common.ts
• frontend/src/i18n/locales/ko/common.ts