fix: restore forced install phase for linux native bindings

supportedArchitectures alone is not sufficient; force reinstall is
needed to fetch the correct linux binding at build time.

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

nixpacks.toml

@@ -1,5 +1,8 @@
 [phases.setup]
 nixPkgs = ["nodejs_23", "pnpm"]
 
+[phases.install]
+cmds = ["pnpm install --no-frozen-lockfile --force"]
+
 [phases.build]
 cmds = ["pnpm build"]