fix: Add build output validation to Dockerfile.web

- Verify dist directory exists after build completes
- Provides better error messaging if build outputs are missing
- Prevents silent failures that result in empty COPY commands

infrastructure/docker/Dockerfile.web

@@ -33,6 +33,14 @@ RUN pnpm turbo build --filter="${TURBO_FILTER}..." || \
      ls -la /app/${APP_PATH}/ 2>/dev/null || echo "App path does not exist" && \
      exit 1)
 
+# Verify build output exists before proceeding
+RUN if [ ! -d "/app/${APP_PATH}/dist" ]; then \
+      echo "ERROR: Build output directory not found at /app/${APP_PATH}/dist"; \
+      echo "Contents of /app/${APP_PATH}:"; \
+      ls -la /app/${APP_PATH}/ 2>/dev/null || echo "Directory does not exist"; \
+      exit 1; \
+    fi
+
 FROM nginx:alpine AS runner
 ARG APP_PATH
 COPY infrastructure/nginx/spa.conf /etc/nginx/conf.d/default.conf