fix(ci): add pnpm store prune to Dockerfile and post-deploy checks

Clear pnpm cache before installing dependencies in BuildKit and runner
to fix ERR_PNPM_TARBALL_INTEGRITY when internal packages are republished
with the same version.

Dockerfile

@@ -27,6 +27,7 @@ RUN --mount=type=cache,id=pnpm,target=/pnpm/store \
     export NPM_TOKEN=$(cat /run/secrets/NPM_TOKEN) && \
     echo "@mintel:registry=https://git.infra.mintel.me/api/packages/mmintel/npm" > .npmrc && \
     echo "//git.infra.mintel.me/api/packages/mmintel/npm/:_authToken=\${NPM_TOKEN}" >> .npmrc && \
+    pnpm store prune && \
     pnpm install --no-frozen-lockfile && \
     rm .npmrc