Replace dropdowns with combobox (searchbar + select) whereever needed

**Is your feature request related to a problem? Please describe.**
Currently u have to search for a faculty by scrolling through the list

**Describe the solution you'd like**
Instead of select dropdown use https://ui.shadcn.com/docs/components/combobox combobox to search for and then select the faculty etc

**Additional context**

Example of replacement:

Start by locating the faculty and other select dropdowns in the frontend, then compare their behavior with the linked shadcn combobox example. Replace the relevant dropdowns so users can search for and select faculty entries; done means the intended selectors support both searching and selection without scrolling through the full list.

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