Backend: Create Fetch Saved Projects with Sorting Endpoint

[Vriti62]

Description
This sub-issue covers the backend implementation for fetching a user’s saved projects and providing sorting options.

Users should be able to retrieve their saved collection and sort projects:
-By date added (newest → oldest, oldest → newest)
-By popularity (most liked → least liked)

Tasks / Requirements
-Create an authenticated GET endpoint to fetch all saved projects for the logged-in user.
-Add query parameters to control sorting (sort=date or sort=likes).
-Return paginated results if collections grow large.

refers: #1180

[github-actions]

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