updates to seed fallback behavior

[chadperson]

This pull request introduces several improvements to code quality, configuration, and theming defaults. The most significant changes include updating the JavaScript language version for linting, simplifying Docker volume configuration, and improving how theme images are handled and validated. The changes also ensure that empty or whitespace-only theme image fields are not treated as valid images.

Configuration and Environment Updates:

• Updated the ecmaVersion in .eslintrc.json from 9 to 2020, enabling support for newer JavaScript syntax and features.
• Simplified Docker Compose volume definitions in docker-compose.yml by switching to shorthand syntax for mounting nodemodules and npm volumes, improving readability and maintainability.

Theming and Image Handling Improvements:

• Cleared default image and logo fields in src/lib/defaultTheme.js by setting them to empty strings, ensuring that no placeholder images are used by default.
• Improved the imageSet utility in Theme/FileUpload.jsx to check for non-empty, non-whitespace strings, making image validation stricter.
• Updated the footer in App/Footer.jsx to only render brandLogo2 if it is a non-empty, non-whitespace string, and to trim whitespace before using the value.