chore: unify action names

.github/workflows/backend-tests.yml

-name: Backend Test
+name: Backend Tests
 
 on:
   push:

.github/workflows/build-and-push-stable-image.yml

-name: Build and Push Stable Docker Image
+name: Build and Push Stable Image
 
 on:
   push:

.github/workflows/demo-render-deploy.yml

-name: Deploy Demo to Render
+name: Demo Render Deploy
 
 on:
   workflow_dispatch:

.github/workflows/frontend-tests.yml

-name: Frontend Test
+name: Frontend Tests
 
 on:
   push:

.github/workflows/proto-linter.yml

-name: Protobuf Linter
+name: Proto Linter
 
 on:
   push:

.github/workflows/stale.yml

-name: Close Stale Issues
+name: Stale
 
 on:
   schedule: