Add google-cloud-aiplatform dependency to requirements.txt

Author: smirk-dev

backend/requirements.txt

@@ -12,6 +12,7 @@ python-multipart>=0.0.6
 google-generativeai>=0.8.0
 google-cloud-firestore>=2.16.0
 google-cloud-storage>=2.14.0
+google-cloud-aiplatform>=1.43.0
 google-auth>=2.25.0
 
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