[server] Recognize Hadoop missing snapshot files

[wolfkill]

Summary

• Treat Hadoop/HDFS File does not exist snapshot download failures as missing snapshot data.
• Reuse the existing broken snapshot cleanup/fallback path in coordinator recovery and replica snapshot download.
• Add regression coverage for the Hadoop error message and wrapped causes.

Fixes #3740

Test Plan

• JAVA_HOME=/Users/cc/Library/Java/JavaVirtualMachines/corretto-18.0.2/Contents/Home mvn -pl fluss-server -am -Dtest=CompletedSnapshotStoreManagerTest#testMetadataInconsistencyWithHadoopFileDoesNotExistException -DfailIfNoTests=false test
  • RED before fix: failed with FileNotFoundException: File does not exist: /remote/snapshot/CURRENT
  • GREEN after fix: Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
• JAVA_HOME=/Users/cc/Library/Java/JavaVirtualMachines/corretto-18.0.2/Contents/Home mvn -pl fluss-server -am -Dtest=CompletedSnapshotTest,CompletedSnapshotStoreManagerTest#testMetadataInconsistencyWithHadoopFileDoesNotExistException -DfailIfNoTests=false test
  • Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
• git diff --check
• JAVA_HOME=/Users/cc/Library/Java/JavaVirtualMachines/corretto-18.0.2/Contents/Home mvn -pl fluss-server -am -DfailIfNoTests=false test
  • Tests run: 1136, Failures: 0, Errors: 0, Skipped: 0

🤖 AI-assisted changes - reviewed by human developer