SPA routes return 404 on page refresh

[cameronhotchkies]

Problem

Refreshing the browser on any client-side route (e.g. /app/login, /app/posts/123) returns a 404:

Nothing found at /app.

The WebTabResourceModule in WebAssetsModule.kt serves static files from classpath:/web/ at the /app/ prefix, but has no fallback for SPA routes. When the browser requests a path like /app/posts/123, Misk looks for a matching static file or action, finds none, and returns a 404.

Suggested remedy

Add a catch-all SpaFallbackAction mapped to /app/{path:.*} that serves the index.html from classpath resources for non-asset paths (i.e. paths without a file extension). This allows React Router to handle routing client-side while preserving the URL, so the user lands on the correct page as if they had navigated there within the SPA.

Static asset paths (containing a .) should still return 404 to avoid masking genuinely missing files.

Files to change

• New: src/main/kotlin/.../actions/SpaFallbackAction.kt — catch-all action that loads classpath:/web/index.html and serves it with Content-Type: text/html
• Edit: src/main/kotlin/.../WebAssetsModule.kt — register SpaFallbackAction via WebActionModule.create<SpaFallbackAction>()