feat: add option to download project as zip

[notfawkes]

Is your feature request related to a problem? Please describe:

Currently, there is no straightforward way to export or download a generated project as a complete package. Users must manually copy files or reconstruct the project locally, which is inefficient and error-prone, especially for multi-file or nested structures.

Describe the solution you'd like:

Add a “Download as ZIP” option that allows users to export the entire project as a single compressed archive.

Expected behavior:

1. Packages all project files and folders while preserving structure
2. Works client-side without requiring server-side processing
3. Accessible via a clear UI action (e.g., button in project actions menu)

Describe alternatives you've considered:

1. Manual copy-paste of files → inefficient and not scalable
2. Downloading files individually → breaks workflow for larger projects
3. Git-based export → adds unnecessary complexity for casual users

Additional context:

Key considerations:

1. Must handle nested directories correctly
2. Should support large projects without significant performance degradation
3. Avoid introducing heavy dependencies for ZIP generation
4. Ensure compatibility across major browsers

This feature improves usability by enabling quick project export and local development workflows.