Add S3 configuration options and improved error handling

- Add s3_verify_ssl config option for SSL/TLS verification
- Add s3_connect_timeout and s3_read_timeout config options
- Add s3_max_retries config option with adaptive retry mode
- Add S3StorageUnavailableError for backend availability issues
- Add HashCollisionError for detecting extremely rare hash collisions
- Add hash collision detection by comparing file sizes on dedup
- Handle network interruption and timeout errors explicitly
- Update routes.py to handle new exception types with appropriate HTTP codes

backend/app/routes.py

@@ -29,6 +29,8 @@ from .storage import (
     HashComputationError,
     S3ExistenceCheckError,
     S3UploadError,
+    S3StorageUnavailableError,
+    HashCollisionError,
 )
 from .models import (
     Project,
@@ -998,6 +1000,19 @@ def upload_artifact(
             status_code=503,
             detail="Storage service temporarily unavailable. Please retry.",
         )
+    except S3StorageUnavailableError as e:
+        logger.error(f"S3 storage unavailable: {e}")
+        raise HTTPException(
+            status_code=503,
+            detail="Storage backend is unavailable. Please retry later.",
+        )
+    except HashCollisionError as e:
+        # This is extremely rare - log critical alert
+        logger.critical(f"HASH COLLISION DETECTED: {e}")
+        raise HTTPException(
+            status_code=500,
+            detail="Data integrity error detected. Please contact support.",
+        )
     except StorageError as e:
         logger.error(f"Storage error during upload: {e}")
         raise HTTPException(status_code=500, detail="Internal storage error")