fix: Fix PostCSS config and Dockerfile

1. Rename postcss.config.js to postcss.config.cjs
   - Fixes CommonJS syntax in ES module project
   - Allows build to complete successfully

2. Remove --production flag from Dockerfile
   - Install ALL dependencies including sharp
   - Sharp required for Astro image optimization
   - Fixes sharp missing error

Both fixes enable successful Docker build and favicon to work.

Dockerfile

@@ -6,13 +6,14 @@ WORKDIR /app
 # Copy package files
 COPY package*.json ./
 
-# Install dependencies
+# Install ALL dependencies (including sharp for image optimization)
 RUN npm ci
 
 # Copy source code
 COPY . .
 
 # Build the project
+# Astro automatically copies public/ to dist/
 RUN npm run build
 
 # Production Stage
@@ -23,13 +24,11 @@ WORKDIR /app
 # Copy package files
 COPY package*.json ./
 
-# Install production dependencies only
-RUN npm ci --production
+# Install ALL dependencies (sharp is required for Astro image optimization)
+RUN npm ci
 
-# Copy built assets from builder
+# Copy ONLY dist folder (contains build + public assets like favicon)
 COPY --from=builder /app/dist ./dist
-COPY --from=builder /app/public ./public
-COPY --from=builder /app/astro.config.mjs ./
 
 # Expose port
 EXPOSE 4321