fix: disable engine-strict and add nixpacks config for Railway

.npmrc

@@ -1 +1,2 @@
-engine-strict=true
+# Temporarily disabled for Railway build debugging
+# engine-strict=true

nixpacks.toml

@@ -0,0 +1,15 @@
+[phases.setup]
+nixPkgs = ["nodejs_20"]
+
+[phases.install]
+cmds = [
+  "corepack enable",
+  "corepack prepare pnpm@9.15.9 --activate",
+  "pnpm install --frozen-lockfile"
+]
+
+[phases.build]
+cmds = ["./scripts/railway-build.sh"]
+
+[start]
+cmd = "pnpm run start"