fix(s3): check both 'Policy' and 'policy' field names in presigned POST

The AWS SDK sends the presigned POST policy field as 'Policy' (capital P),
but the validation code was looking for 'policy' (lowercase). This caused
policy condition validation to be silently skipped for all presigned POST
uploads made via the AWS SDK.

Now checks both 'Policy' and 'policy' for compatibility.

Co-Authored-By: Matej Snuderl <ematej.snuderl@gmail.com>

Author: devin-ai-integration[bot]

src/main/java/io/github/hectorvent/floci/services/s3/S3Controller.java

@@ -1560,7 +1560,10 @@ private Response handlePresignedPost(String bucket, String contentType, byte[] b
         }
 
         // Validate policy conditions if present
-        String policy = fields.get("policy");
+        String policy = fields.get("Policy");
+        if (policy == null) {
+            policy = fields.get("policy");
+        }
         if (policy != null && !policy.isEmpty()) {
             validatePolicyConditions(policy, bucket, fields, fileData.length);
         }