[Bug]: spannerchangestreamstobigquery - Spanner UUID columns types cause errors in pipeline

### Related Template(s)

Spanner change streams to BigQuery template

### Template Version

2026-03-10-00_rc00

### What happened?

Create a Spanner table with UUID
Create a change stream listening to that table
Start a Spanner change streams to BigQuery template
Error in log (see below)h
(both PostgreSQL and GoogleSQL dialects

### Relevant log output

```shell
Error message from worker: generic::unknown: org.apache.beam.sdk.util.UserCodeException: java.lang.RuntimeException: java.lang.RuntimeException: Caught exception when constructing SpannerColumn for each column tracked by change stream test_uuid_stream, message: Optional[Unsupported Spanner PostgreSQL type: uuid], cause: null
org.apache.beam.sdk.util.UserCodeException.wrap(UserCodeException.java:39)
com.google.cloud.teleport.v2.templates.spannerchangestreamstobigquery.FailsafeModJsonToTableRowTransformer$FailsafeModJsonToTableRow$FailsafeModJsonToTableRowFn$DoFnInvoker.invokeSetup(Unknown Source)
org.apache.beam.sdk.transforms.reflect.DoFnInvokers.tryInvokeSetupFor(DoFnInvokers.java:53)
org.apache.beam.fn.harness.FnApiDoFnRunner.(FnApiDoFnRunner.java:440)
org.apache.beam.fn.harness.FnApiDoFnRunner$Factory.addRunnerForPTransform(FnApiDoFnRunner.java:180)
```