fix: make screenshot upload optional when IMGBB_API_KEY is unavailable (for forks)

Author: boorad

.github/actions/post-maestro-screenshot/action.yml

@@ -14,7 +14,7 @@ inputs:
     default: 'unknown'
   imgbb-api-key:
     description: 'ImgBB API key for image hosting'
-    required: true
+    required: false
 
 runs:
   using: 'composite'
@@ -69,7 +69,7 @@ runs:
         fi
 
     - name: Upload screenshot to ImgBB
-      if: steps.check-screenshot.outputs.exists == 'true' && github.event_name == 'pull_request'
+      if: steps.check-screenshot.outputs.exists == 'true' && github.event_name == 'pull_request' && inputs.imgbb-api-key != ''
       id: upload-screenshot
       uses: McCzarny/upload-image@v2.0.0
       with: