Add Loading States for All Backend Requests

[nidhi-k3]

Show spinners/loading messages while waiting for backend to respond.

What to do:
When uploading drone images, show "Uploading..." with a spinner
When processing (backend is creating charts), show the loading screen
When loading results, show "Loading results..."
When loading projects list, show "Loading projects..."

[Ar-temis]

Wait, I'll improve this and give the frontend like what the status of the process is at

[nidhi-k3]

Okay! Right now, I have a spinner that goes on until everything is complete.