[Bug]: The course catalogue only ever shows the first 12 courses, and the search box only searches those

[MOHITKOURAV01]

Summary

#43 made GET /api/user/getallcourses paginated, searchable and filterable on the server. The catalogue never picked any of it up. frontend/src/components/common/AllCourses.jsx still calls the endpoint bare:

const res = await axiosInstance.get("/api/user/getallcourses");
setAllCourses(res.data.data || []);

normalizePagination in backend/utils/pagination.js defaults to DEFAULT_LIMIT = 12, so the response contains 12 courses. The component then filters those 12 in a useMemo, and res.data.pagination is dropped on the floor.

Expected result

• Every published course is reachable from the catalogue.
• The search box searches the whole catalogue, not just the loaded page.
• The Free/Paid filter filters the whole catalogue.
• The result count reflects the number of matching courses, not the number of matching rows in the current page.
• There is some way to move between pages.

Actual result

• The 13th course and everything after it is invisible and cannot be enrolled in. There is no page control anywhere in the UI.
• Searching for a course that exists but sits on page 2 shows "No courses match that search".
• The {count} courses found counter maxes out at 12 and is wrong the moment there are more courses than that.
• The Free/Paid filter uses /\d/.test(course.C_price), which classifies a course priced "Free for the first 100" as paid, while the server's FREE_PRICE_PATTERN gets it right. The two disagree.
• Every keystroke re-filters an array the server already knows how to filter, and no request is ever made after the first mount.

Steps to reproduce

1. Seed more than 12 courses (node backend/seed.js, then add a few, or insert directly).
2. Open the catalogue on the home page.
3. Count the cards — 12, regardless of how many exist.
4. Type the exact title of the 15th course into the search box → "No courses match that search".
5. Open DevTools → Network. Nothing is requested while typing; only the single mount request is ever sent.
6. curl 'http://localhost:5000/api/user/getallcourses?page=2' returns the missing courses, so the data is there and the API works.

Notes

• The server already accepts page, limit, search, category, educator, priceType and sort, and returns pagination: { page, limit, totalItems, totalPages, hasNextPage, hasPreviousPage }. The fix is on the client.
• Typing needs to be debounced, otherwise the search box fires a request per keystroke.
• A request that resolves after a newer one must not overwrite the newer results; the component needs to ignore stale responses.
• The same page is rendered for signed-out visitors on / and for signed-in users through UserHome, so the paging controls have to work in both.