fix: skip PatchTritonVAE registration when triton is not installed

[hcwhan]

Summary

• Check whether the triton package is available before importing PatchTritonVAE
• Avoid startup warning tracebacks on non-CUDA environments (e.g. AMD ROCm) where Triton is not installed
• When Triton is missing, log an info message and skip the node registration instead of attempting import

Motivation

PatchTritonVAE depends on Triton, which is typically unavailable outside NVIDIA CUDA setups. The current unconditional import attempt triggers a warning with full traceback on every startup, even though the node cannot be used in those environments.

Test plan

• Start ComfyUI without Triton installed: no warning traceback; info log about skipping PatchTritonVAE
• Start ComfyUI with Triton installed: PatchTritonVAE node still registers normally
• Other KJNodes nodes continue to load as before