fix(build): ditch corepack in containerfile

The deploy pipeline was failing on container builds (across the PL
frontend repos) due to upstream breakage in corepack [0].
This changes matches changes in e.g. [1], [2].

[0] nodejs/corepack#612
[1] penumbra-zone/penumbers#19
[2] penumbra-zone/dex-explorer#341

apps/web/Containerfile

@@ -1,13 +1,14 @@
 # slimmest image. only for running the container.
-FROM docker.io/library/node:20-alpine AS alpine
+ARG NODE_MAJOR_VERSION=22
+FROM docker.io/library/node:${NODE_MAJOR_VERSION}-alpine AS base
 LABEL maintainer="[email protected]"
 
-# provide pnpm globally for dep installing and building
-FROM alpine AS base
 ENV NEXT_TELEMETRY_DISABLED=1
 ENV PNPM_HOME="/pnpm"
 ENV PATH="$PNPM_HOME:$PATH"
-RUN corepack enable pnpm
+# We no longer use `corepack enable pnpm` due to breakage documented in
+# https://github.com/nodejs/corepack/issues/612
+RUN npm install -g pnpm@${PNPM_VERSION}
 RUN pnpm install turbo --global
 
 # prune package structure + code into out/
@@ -44,7 +45,7 @@ COPY turbo.json turbo.json
 RUN turbo run build --filter=cuiloa-app
 
 # Run container
-FROM alpine AS runner
+FROM base AS runner
 WORKDIR /app
 
 # Disable telemetry.