Add Cypress workspace image edit flow

[cybercraftsolutionsllc]

Summary

• add Cypress coverage for editing an organization/workspace image through the edit modal file input
• use an in-memory PNG so the spec does not need a binary fixture
• assert the selected image preview appears before saving the updated workspace

Closes #428.

Validation

• npx tsc --noEmit --target es2015 --types cypress,node --moduleResolution node cypress\global.d.ts cypress\e2e\27_editOrganizationImage.cy.ts
• npx eslint cypress\e2e\27_editOrganizationImage.cy.ts --max-warnings 100
• git diff --check