Dockerfile: change as to AS

Author: cpprian

backend/Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.13-slim as builder
+FROM python:3.13-slim AS builder
 
 ENV PYTHONUNBUFFERED=1 \
     PYTHONDONTWRITEBYTECODE=1 \
@@ -24,7 +24,7 @@ COPY pyproject.toml poetry.lock ./
 
 RUN poetry install --no-dev --no-root --no-interaction --no-ansi
 
-FROM python:3.13-slim as runtime
+FROM python:3.13-slim AS runtime
 
 ENV PYTHONUNBUFFERED=1 \
     PYTHONDONTWRITEBYTECODE=1 \