Pin the Docker image

Exercism's policy is to prefer pinned versions.
Using the same hash across all runners allows us to store and reuse the same image, rather than needing to store a per-runner base image. This helps cut down on storage costs.

Author: IsaacG

Dockerfile

@@ -6,7 +6,7 @@
 # to keep this in sync between the two images. A slight mismatch in these layers
 # would lead to douple the storage requirement on Exercism's servers.
 
-FROM rust:1.95.0 AS build-local-registry
+FROM rust:1.95.0-trixie@sha256:a9cfb755b33f5bb872610cbdb25da61f527416b28fc9c052bbce4bef93e7799a AS build-local-registry
 
 WORKDIR /work
 COPY local-registry/Cargo.toml .
@@ -46,7 +46,7 @@ EOF
 ############################## END SHARED LAYERS ##############################
 
 
-FROM rust:1.95.0 AS build
+FROM rust:1.95.0-trixie@sha256:a9cfb755b33f5bb872610cbdb25da61f527416b28fc9c052bbce4bef93e7799a AS build
 
 WORKDIR /work
 COPY Cargo.* ./