Fix Aria SDK version logging in websocket bridge

Summary:
`_log_startup_header()` in `websocket_bridge.py` was logging `Aria SDK : version unavailable` on every startup because it attempted `import projectaria_client_sdk` — which is the PyPI *distribution* name, not the importable module. The Client SDK installs as the `aria` package, so the import always failed and the `except Exception` branch always ran.

Switch to `from aria._version import __version__ as aria_sdk_version`, mirroring what the SDK's own `__cli__.py` and `__gen2_cli__.py` do after D104702929. The startup banner now reports the real installed SDK version instead of `version unavailable`.

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Differential Revision: D107395195

fbshipit-source-id: 2988a0d618c8713bb58e5e0d0148fffb0997c6fe

Author: Ryan Frawley

projectaria_ark_plugin/skills/web-app-creator/web-app-creator-backend/backend/websocket_bridge.py

@@ -50,11 +50,9 @@ def _log_startup_header():
     logger.info(f"Python    : {platform.python_version()} ({platform.machine()})")
     logger.info(f"Platform  : {platform.platform()}")
     try:
-        import projectaria_client_sdk
+        from aria._version import __version__ as aria_sdk_version
 
-        logger.info(
-            f"Aria SDK  : {getattr(projectaria_client_sdk, '__version__', 'unknown')}"
-        )
+        logger.info(f"Aria SDK  : {aria_sdk_version}")
     except Exception:
         logger.info("Aria SDK  : version unavailable")
     logger.info(f"websockets: {websockets.__version__}")