fix: set DEBIAN_FRONTEND=noninteractive for GPU build

Prevents tzdata interactive prompt when installing deadsnakes PPA.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -14,6 +14,8 @@ RUN pip install --no-cache-dir -r /tmp/requirements-cpu.txt && rm /tmp/requireme
 # ---- GPU base ----
 FROM nvidia/cuda:12.4.1-cudnn-runtime-ubuntu22.04 AS base-gpu
 
+ENV DEBIAN_FRONTEND=noninteractive
+
 RUN apt-get update && apt-get install -y --no-install-recommends \
     software-properties-common \
     && add-apt-repository ppa:deadsnakes/ppa \