Add Spark 3.5 Scala 2.13 DBF datasource

[DAChernikov]

Summary

• migrate build to Spark 3.5 / Scala 2.13 with provided Spark, Scala and Hadoop dependencies
• implement read-only DBF DataSource V1 with Hadoop FileSystem access and executor-side reads
• add Scala Spark tests, PySpark assembly smoke checks, jar inspection, docs and release workflows

Local verification

• ./mvnw clean verify
• ./mvnw clean verify -Dspark.version=3.5.2
• ./mvnw clean verify -Dspark.version=3.5.3
• ./mvnw clean package -DskipTests
• scripts/inspect-jar.sh target/spark-dbf_2.13-0.1.0-assembly.jar
• Spark 3.5.4 Scala 2.13 spark-submit PySpark smoke test