Fix Docker build: replace workspace:* with file: references

npm doesn't support the `workspace:*` protocol (that's pnpm/Yarn).
This caused `npm install` to fail with EUNSUPPORTEDPROTOCOL during
Docker builds. Replaced both occurrences with `file:` relative paths
that npm workspaces resolves correctly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -25,7 +25,7 @@
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
     "zod": "^3.24.0",
-    "@dynamic-sites/shared": "workspace:*"
+    "@dynamic-sites/shared": "file:shared"
   },
   "devDependencies": {
     "@types/react": "^19.1.2",