0.5.2 - CUDA runtime slimming and launch-blocking removal

CUDA runtime slimming and a throughput fix. No application code or dependency pin changed.

• cuda-toolkit-12-2 replaced by cuda-libraries-12-2. The toolkit brought the compiler, Nsight Systems, dev headers and documentation, none used at runtime. ctranslate2 loads libcudart, libcublas and libcudnn dynamically and torch carries its own CUDA libraries from pip, so cuda-libraries-12-2 plus libcudnn9-cuda-12 is the complete runtime set. cuda-runtime-12-2 was deliberately not used: it depends on cuda-drivers.
• CUDA_LAUNCH_BLOCKING=1 removed. It forced every kernel launch to be synchronous on all five Whisper passes.
• Expected side effect: the Trivy gate loses the 64 findings that lived in the Nsight Systems Go binary.

Validated on the GPU host against the reference file; per-pass timings versus the 0.4.0 baseline are in docs/SESSION_KNOWLEDGE.md.