Fixed actions to work only with new PR to main

.github/workflows/lint.backend.yml

@@ -1,7 +1,9 @@
 name: Lint Moonstream backend
 
 on:
-  push:
+  pull_request:
+    branches:
+      - "main"
     paths:
       - "backend/**"
 

.github/workflows/lint.crawlers.yml

@@ -1,7 +1,9 @@
 name: Lint Moonstream crawlers
 
 on:
-  push:
+  pull_request:
+    branches:
+      - "main"
     paths:
       - "crawlers/**"
 

.github/workflows/lint.db.yml

@@ -1,7 +1,9 @@
 name: Lint Moonstream db
 
 on:
-  push:
+  pull_request:
+    branches:
+      - "main"
     paths:
       - "db/**"
 

.github/workflows/lint.frontend.yml

@@ -1,9 +1,6 @@
 name: Build Moonstream frontend
 
 on:
-  push:
-    paths:
-      - "frontend/**"
   pull_request:
     branches:
       - "main"