fix: add build args to Dockerfile for Hugging Face environment variables

- Add ARG statements to accept Hugging Face variables as build args
- Promote build args to ENV variables for build-time access
- Fixes astro:env/client build error on Hugging Face Spaces
- Ensures SUPABASE_URL and SUPABASE_ANON_KEY are available during build

Dockerfile

@@ -2,6 +2,14 @@ FROM node:18-alpine
 
 WORKDIR /app
 
+# Accept Hugging Face Variables as build args
+ARG SUPABASE_URL
+ARG SUPABASE_ANON_KEY
+
+# Expose them to the build environment
+ENV SUPABASE_URL=$SUPABASE_URL
+ENV SUPABASE_ANON_KEY=$SUPABASE_ANON_KEY
+
 # Copy package files
 COPY package*.json ./