force workflow to use offline mode

.github/workflows/backend.yml

@@ -35,9 +35,13 @@ jobs:
       
       - name: Build
         run: cargo build
+        env:
+          SQLX_OFFLINE: "true"
   
       - name: Run tests
         run: cargo test
+        env:
+          SQLX_OFFLINE: "true"
 
   lint:
     runs-on: ubuntu-latest
@@ -57,6 +61,8 @@ jobs:
   
       - name: Check clippy for new warnings
         run: cargo clippy
+        env:
+          SQLX_OFFLINE: "true"
   
 
   schema-check: