fix: Iceberg warehouse path mismatch between Python and Java/Scala catalogs

[aglinxinyuan]

What changes were proposed in this PR?

Iceberg tables created via the Python API could not be read back on the Java/Scala side because the two runtimes were registering the Postgres JDBC catalog with different warehouse values, which PyIceberg persists into the table metadata.

The Python side (create_postgres_catalog in amber/src/main/python/core/storage/iceberg/iceberg_utils.py) was prefixing the same path with file://, so tables created by Python UDFs were registered under file:///... while Scala-side lookups expected the un-prefixed path.

This caused subsequent reads of Python-written Iceberg tables to fail (wrong/unresolvable warehouse path in the metadata pointer).

Drop the file:// prefix in create_postgres_catalog so Python matches the Scala catalog's warehouse value exactly. PyIceberg accepts a plain local path here and will treat it as a local filesystem warehouse, consistent with the Scala JdbcCatalog configuration.

Any related issues, documentation, discussions?

Closes #4408

How was this PR tested?

Added a test case and tested manually:

1. Create an Iceberg table from a Python UDF operator and confirm it can be read back from the Scala/Java engine in the same workflow.
2. Re-run existing Iceberg-backed workflows (Python-write → Python-read and Python-write → Scala-read) and confirm no regressions.
3. Verify on Windows that the warehouse path passed in (with colon stripped) still resolves correctly from Python.

Was this PR authored or co-authored using generative AI tooling?

No.

[Copilot]

Pull request overview

Fixes an Iceberg interoperability bug where Python-created tables could not be read by the Java/Scala engine due to a mismatched Postgres JDBC catalog warehouse value.

Changes:

• Align PyIceberg SqlCatalog warehouse configuration with the Java/Scala JdbcCatalog by removing the file:// prefix.
• Ensure Iceberg table metadata written from Python uses the same warehouse string the Scala side expects.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Xiao-zhen-Liu]

LGTM