Add Stage File Proxy module to Varbase Dev Base recipe

Problem/Motivation

Development environments often require access to production or staging files without manually syncing the entire sites/default/files directory. This is especially important for media-heavy Varbase sites where downloading all assets is slow and unnecessary.

The Stage File Proxy module allows development environments to automatically fetch missing files from a remote origin (such as production or staging) on demand. This significantly improves developer experience and reduces setup time.

Proposed resolution

• Add drupal/stage_file_proxy to in the composer.json file.
• Optional in local dev env. ( DDEV ) Allow developers to configure remote origin for file fallback.

This improves developer workflow and reduces the need for full file syncs.

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ✅ Automated unit/functional testing coverage
• ✅ Developer Documentation support on feature change/addition
  
  Varbase Development Base
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes
• ❌ Release varbase-11.0.0-alpha1, varbase_starter-1.0.0-alpha1, varbase_dev_base-1.0.0-alpha1

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• feat: #3586274 Add Stage File Proxy module to Varbase Dev Base recipe