Substrait physical plan import should not accept arbitrary local file paths

### Describe the bug

When importing a Substrait physical plan containing `ReadRel.LocalFiles`, DataFusion builds a Parquet scan against `ObjectStoreUrl::local_filesystem()` and copies the plan-provided `UriPath` / `UriPathGlob` / `UriFile` / `UriFolder` value into `ObjectMeta.location` without a host-supplied root or object-store policy check.

In embeddings that accept Substrait physical plans from lower-trust callers, this can allow the imported plan to select process-local Parquet files outside the host's intended dataset roots.

Relevant code path on current `main`:

- `datafusion/substrait/src/physical_plan/consumer.rs`: `FileScanConfigBuilder::new(ObjectStoreUrl::local_filesystem(), ...)`
- `datafusion/substrait/src/physical_plan/consumer.rs`: cloned Substrait path becomes `ObjectMeta { location: path.into(), ... }`
- the configured scan is returned as `DataSourceExec::from_data_source(...)`

### To Reproduce

1. Import a Substrait physical plan using `ReadRel.LocalFiles` for a Parquet read.
2. Set the file path in the serialized plan to a local path selected by the plan submitter.
3. Execute the returned physical plan in a host process that accepts the imported plan.

I am intentionally not including a full payload in the public issue. The static source path above is enough to identify the behavior.

### Expected behavior

Imported physical plans should not be able to directly choose arbitrary process-local filesystem paths unless the embedding host explicitly supplies that policy. Possible fixes include rejecting absolute/traversing paths, requiring an allowlisted root or object-store binding during physical plan import, or resolving imported file references through registered catalog/object-store policy rather than hard-coding the local filesystem.

### Additional context

This came from a local security review of Apache DataFusion at revision `38269f9c0cf1a80897aee588ea2daebe0aba4f6b`. The impact depends on an embedding host exposing Substrait physical plan import across a trust boundary; DataFusion itself does not ship a standalone server/auth boundary in this repository.

Start in datafusion/substrait/src/physical_plan/consumer.rs and trace ReadRel.LocalFiles through FileScanConfigBuilder::new and the ObjectMeta location conversion. Compare the import behavior with the host's object-store or path policy, then add coverage showing that an imported plan cannot select arbitrary local paths unless explicitly permitted.

Written by the indexing model from the issue text.