[auth] Add Lint validation for custom icon name

.github/workflows/auth-lint.yml

@@ -33,5 +33,15 @@ jobs:
 
             - run: flutter analyze --no-fatal-infos
 
+            - name: Verify custom icons are lowercase including optional understores, and end with .svg
+              run: |
+                  find assets/custom-icons -type f -name "*.svg" | while read -r file; do
+                      if [[ "$(basename "$file")" != "$(basename "$file" | tr '[:upper:]' '[:lower:]' | tr ' ' '_')" ]]; then
+                          echo "File name is not lowercase: $file"
+                          exit 1
+                      fi
+                  done
+              
+
             - name: Verify custom icon JSON
               run: cat assets/custom-icons/_data/custom-icons.json | jq empty