chore: update github action trigger

.github/workflows/backend-tests.yml

 name: Backend Test
 
 on:
+  push:
+    branches: [main]
   pull_request:
     branches:
       - main

.github/workflows/frontend-tests.yml

 name: Frontend Test
 
 on:
+  push:
+    branches: [main]
   pull_request:
     branches:
       - main

.github/workflows/proto-linter.yml

 name: Proto linter
 
 on:
+  push:
+    branches: [main]
   pull_request:
     branches:
       - main