Unified Project: Single Project and Settings for Volto/Classic projects

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This PR completes the unification of the monorepo and classic templates

Summary of Changes

• Implemented a "Safe Default + Prompt Override" pattern in cookieplone.json: static defaults are provided at the top level to ensure context presence, while dynamic prompts are handled within the allOf conditional block.

• Guarded Frontend Mentions: Added Jinja2 guards to the generated README.md and other files to ensure that frontend-specific sections only appear when feature_headless is enabled.

• Enhanced Test Coverage:

  • Added tests/templates/projects/monorepo/test_project_classic.py to explicitly verify Classic UI project generation (checking for the absence of the frontend folder and presence of correct metadata).
  • Updated tests/templates/projects/monorepo/test_project_variables.py to match the current set of expected variables.
  • Template Robustness: Verified that all 297 tests for the monorepo template now pass in both Headless and Classic modes.

Key Files Affected

• templates/projects/monorepo/cookieplone.json: Main project schema and logic.
• templates/projects/monorepo/{{ cookiecutter.__folder_name }}/README.md: Protected frontend-related strings.
• tests/templates/projects/monorepo/test_project_classic.py: New verification suite for Classic mode.
• tests/templates/projects/monorepo/test_project_variables.py: Updated variable assertions.