fix(docker): add pnpm global bin to PATH in frontend build stage

pnpm 11 installs globally-added binaries to $PNPM_HOME/bin and treats that
directory being absent from PATH as a hard error, so `pnpm add -g license-checker`
in the frontend-compiler stage failed ("global bin directory is not in PATH")
whenever the frontend layer cache was invalidated. Prepend $PNPM_HOME/bin to PATH.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Dockerfile

@@ -10,7 +10,7 @@ ENV NODE_ENV=production
 ENV VITE_BUILD_MEMORY_LIMIT=4096
 ENV NODE_OPTIONS="--max-old-space-size=4096"
 ENV PNPM_HOME="/usr/local/share/pnpm"
-ENV PATH="$PNPM_HOME:$PATH"
+ENV PATH="$PNPM_HOME/bin:$PNPM_HOME:$PATH"
 
 WORKDIR /app/ui