add workflow dispatch to process single user

Author: ericahan22

.github/workflows/process-single-user.yml

@@ -1,9 +1,15 @@
 name: Process Single User
-run-name: Process @${{ github.event.client_payload.username }}
+run-name: Process @${{ github.event.client_payload.username || inputs.username }}
 
 on:
   repository_dispatch:
     types: [new_instagram_post]
+  workflow_dispatch:
+    inputs:
+      username:
+        description: 'Instagram username to process'
+        required: true
+        type: string
 
 jobs:
   process-post:
@@ -36,7 +42,7 @@ jobs:
       EMAIL_HASH_KEY: ${{ secrets.EMAIL_HASH_KEY }}
       # --- Apify Token ---
       APIFY_API_TOKEN: ${{ secrets.APIFY_API_TOKEN }}
-      TARGET_USERNAME: ${{ github.event.client_payload.username }}
+      TARGET_USERNAME: ${{ github.event.client_payload.username || inputs.username }}
       MAX_CONCURRENT_TASKS: 1
 
     steps: