Connecting cost to backend

[janekamata]

ℹ️ Issue

Closes #370

📝 Description

Write a short summary of what you added. Why is it important? Any member of C4C should be able to read this and understand your contribution -- not just your team members.

Briefly list the changes made to the code:

1. Updated processCashflow files with cost edit/delete endpoints
2. Connected cost KPI card to backend value
3. Updated source list, editlineitem to save edits/deletes
4. Added CashEditCost for cost edit form
5. Updated category dropdown and thus add cost/revenue to take in onChange correctly
6. Updating navbar and mainpage routes to guard cashflow for admin only

✔️ Verification

What steps did you take to verify your changes work? These should be clear enough for someone to be able to clone the branch and follow the steps themselves.

Testing on local build

Provide screenshots of any new components, styling changes, or pages.

Test Changes

If your new feature required some test to be changed or added to fit the new functionality or changes please document these changes here.

🏕️ (Optional) Future Work / Notes

Did you notice anything ugly during the course of this ticket? Any bugs, design challenges, or unexpected behavior? Write it down so we can clean it up in a future ticket!

• Adding revenue
• Abstracting out to apply for both cost/revenue and integrate with add cost/revenue
• Updating chart and chart kpis with cost/revenue