feat(planet): implement progressive loading for project cards

[subhraneel2005]

Summary

Implements progressive loading while fetching Planet server projects in Global. Projects now appear incrementally as they load instead of waiting for all the 25 API requests to complete.
Fixes #6072

PR Category

• Bug Fix
• Feature
• Performance
• Tests
• Documentation

Problem

When scrolling to load more projects in Global:

1. downloadProjectList returns ~25 project IDs
2. Code makes 25 separate getProjectDetails API calls
3. UI waits for ALL requests to complete before showing anything
4. Users sees loader for 5-10 seconds

Solution

Modified GlobalPlanet.js to render each project card immediately after its details are fetched:

• Added renderSingleProject(id) - renders individual card without clearing container
• Modified downloadProjectsToCache() - accepts onEachComplete and onAllComplete callbacks
• Modified addProjectToCache() - triggers render immediately on each completion
• Updated addProjects() - uses progressive callbacks

Benefits

• Immediate feedback (first project visible within ~200ms)
• Better perceived performance
• No breaking changes to API
• Follows progressive loading UX pattern

Testing

• Verified cards appear one-by-one as they load
• Load More button still works correctly
• Cached projects still render immediately
• Search functionality unaffected
• All Jest tests passed
• No linting issues

Attachments

Before: Loading spinner shows for several seconds, then all cards appear at once

mar.4.2026.14_41.mp4

After: Cards appearing one-by-one as they load

mar.4.2026.14_54.mp4

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.