feat(node): support conditional SPA index fallback (#582)

* fix(caddy): standardize and improve security in Caddyfile templates

- Standardize security headers and compression settings across Node and static file providers.
- Improve health check handling by using log_skip to reduce log noise.
- Implement custom error page support for static file deployments.
- Update documentation to reflect the default Caddyfile capabilities.
- Add Railway proxy range to trusted proxies for improved network compatibility.

Generated-by: aiautocommit

* test(example): add node-astro-static-404 reproduction case

- Create a new example project to reproduce static site behavior with custom 404 pages.
- Configure Staticfile with index_fallback set to false to test 404 handling.
- Include an integration test suite validating that unknown routes correctly return the custom 404 page.

Generated-by: aiautocommit

* feat(node): support conditional SPA index fallback

- Allow the Caddy configuration to disable index.html fallback for node SPA deployments.
- Expose an option to read `index_fallback` from a Staticfile, defaulting to true for Node SPA projects.

Generated-by: aiautocommit

* docs: document Staticfile index_fallback configuration for Node SPAs

Generated-by: aiautocommit

* test: update snapshot

* Revert "fix(caddy): standardize and improve security in Caddyfile templates"

This reverts commit 6c8f57f5149ca1cc84d04d8eded8cdf7a928a66d.

* refactor: rename static-404 example to spa-staticfile

- Renamed the node-astro-static-404 example to node-spa-staticfile to better reflect its purpose as a SPA configuration example.
- Added a readme explaining the use case for customizing SPA behavior via a Staticfile.

Generated-by: aiautocommit

* refactor(node): update SPA detection and deployment configuration

*   Include Expo in SPA detection logic to ensure consistent behavior.
*   Standardize framework naming capitalization.
*   Update index fallback lookup to use a generalized helper function.

Generated-by: aiautocommit

* refactor(staticfile): align index fallback logic with provider requirements

- Centralize index fallback resolution in GetIndexFallback to differentiate between user-defined values and defaults.
- Update the Staticfile provider to explicitly set the default to false while maintaining compatibility for node SPA implementations.
- Improve Caddyfile template documentation regarding SPA routing behavior.

Generated-by: aiautocommit

* chore: update build plan dependencies and environment variables

- Bump railpack-builder and runtime versions to 2026.6.11
- Update Caddy version to 2.11.4
- Add NPM_CONFIG_FETCH_RETRIES to node environment variables
- Improve Caddyfile SPA routing logic
- Rename snapshot file to reflect the correct test case target

Generated-by: aiautocommit

* test: update Caddyfile try_files comments in snapshots

Generated-by: aiautocommit

* feat(node): treat expo start as a default command

- Add DefaultExpoStartCommand constant to identify the default Expo start script.
- Update hasCustomStartCommand to exclude Expo's default command from the custom command check.
- Update tests to reflect that Expo default behavior is no longer considered custom.

Generated-by: aiautocommit

* test: update snapshot

examples/node-spa-staticfile/.gitignore

@@ -0,0 +1,24 @@
+# build output
+dist/
+
+# generated types
+.astro/
+
+# dependencies
+node_modules/
+
+# logs
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+
+# environment variables
+.env
+.env.production
+
+# macOS-specific files
+.DS_Store
+
+# jetbrains setting folder
+.idea/

examples/node-spa-staticfile/Staticfile

@@ -0,0 +1 @@
+index_fallback: false

examples/node-spa-staticfile/astro.config.mjs

@@ -0,0 +1,5 @@
+// @ts-check
+import { defineConfig } from "astro/config";
+
+// https://astro.build/config
+export default defineConfig({});

examples/node-spa-staticfile/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "node-astro-static-404",
+  "private": true,
+  "type": "module",
+  "version": "0.0.1",
+  "scripts": {
+    "dev": "astro dev",
+    "build": "astro build",
+    "preview": "astro preview",
+    "astro": "astro"
+  },
+  "dependencies": {
+    "astro": "^5.13.7"
+  }
+}

examples/node-spa-staticfile/readme.md

@@ -0,0 +1 @@
+Ensures that a SPA with a Staticfile can customize SPA-related configuration, just like the Staticfile provider.

examples/node-spa-staticfile/src/layouts/layout.astro

@@ -0,0 +1,19 @@
+---
+interface Props {
+  title: string;
+}
+
+const { title } = Astro.props;
+---
+
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>{title}</title>
+  </head>
+  <body>
+    <slot />
+  </body>
+</html>

examples/node-spa-staticfile/src/pages/404.astro

@@ -0,0 +1,9 @@
+---
+import Layout from "../layouts/layout.astro";
+---
+
+<Layout title="404">
+  <main>
+    I'm a 404 page
+  </main>
+</Layout>

examples/node-spa-staticfile/src/pages/index.astro

@@ -0,0 +1,9 @@
+---
+import Layout from "../layouts/layout.astro";
+---
+
+<Layout title="Test Static">
+  <main>
+    HI I'M THE HOME PAGE
+  </main>
+</Layout>

examples/node-spa-staticfile/test.json

@@ -0,0 +1,19 @@
+[
+  {
+    "httpCheck": {
+      "path": "/",
+      "expected": 200,
+      "internalPort": 80,
+      "expectedOutput": "HI I'M THE HOME PAGE"
+    }
+  },
+  {
+    // Reproduces https://github.com/railwayapp/railpack/issues/553
+    // Staticfile index_fallback: false should return 404 for unknown paths (not index.html)
+    "httpCheck": {
+      "path": "/21312",
+      "expected": 404,
+      "internalPort": 80
+    }
+  }
+]

examples/node-spa-staticfile/tsconfig.json

@@ -0,0 +1,5 @@
+{
+  "extends": "astro/tsconfigs/strict",
+  "include": [".astro/types.d.ts", "**/*"],
+  "exclude": ["dist"]
+}