Default to latest Holoscan SDK version (3.9.0)

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## Summary by CodeRabbit

* **Chores**
* Updated the minimum required Holoscan SDK version to 3.9.0 across all
project templates and dependency specifications
* Upgraded default base image and Docker containers to use Holoscan SDK
3.9.0 for consistent build and test environments
* Updated test infrastructure to validate compatibility with Holoscan
SDK 3.9.0

* **Documentation**
* Updated configuration documentation and references to reflect the new
Holoscan SDK 3.9.0 version standard

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>

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Signed-off-by: Tom Birdsong <tbirdsong@nvidia.com>