feat: add filter to courseflow

[Triet-coder]

Description

• Added filter properties for Level, Year, Teaching Period, and Specialization
• Methods to initialize available options from the units dataset
• Client-side filtering that applies the selected criteria (supports combining multiple filters)
• Drop-down menus for each filter + Clear filters button
• Search works within the currently filtered results
• Responsive grid layout for filters that wraps gracefully on smaller screens

User experience

• Users can select any combination of filters
• Clear all filters with a single click
• Search terms refine the already-filtered set
• Filters show only the available options present in the data:
  • All available levels
  • All available years
  • All teaching periods (by name)
  • All specializations

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

1. Load the Units view.
2. Verify each dropdown contains only options present in the dataset.
3. Select filters individually and in combination; confirm the list updates correctly.
4. Enter a search query; confirm results are restricted to the filtered set.
5. Click Clear filters; confirm:
   • All dropdowns reset
   • Search (if applicable) is cleared or reapplied as designed
   • Full unit list is restored
6. Resize browser window to tablet/mobile widths; verify the filter grid wraps and remains usable.
7. Confirm no console errors and no layout shifts during interaction.

Testing Checklist:

• Tested in latest Chrome

Checklist:

• npm ci
• npm run lint
• npm test
• npm start

[AB-Deakin]

Hi Triet, tested this PR on 24/09 and after messaging you on teams I've tried again 28/09 still unable to get the changes to load or show anything in the courseflow for either of the PRs when tested. You'll need to add some more details into both PRs outlinging the build and testing you've done as there is currently no screenshots or working build shown.