feat: update about page to reflect current features

[RMCampos]

This pull request updates and expands the About page to provide a more comprehensive overview of the app's features and technology stack. It introduces new feature descriptions, updates the technology list to reflect the latest stack, and ensures these changes are available across all supported languages. The About page test coverage is also improved to verify the presence of new sections.

About page enhancements:

• Expanded the About page to list all current features, including dark/light theme support, URL attachments, tagging, public note sharing, Markdown editing, and email confirmation. The technology stack section now details tools like React 19, Vite, React Router 7, and i18next, among others. [1] [2] [3]
• Updated the About page to use a new "Buy me a coffee" link.

Internationalization improvements:

• Added translations for all new feature and technology descriptions in English, Portuguese, Spanish, and Russian translation files. [1] [2] [3] [4]

Testing:

• Enhanced the About page test to verify the presence of the new sections and headings.