fix: add SPA forwarding controller for React Router

[tusharkhatriofficial]

Spring Boot was returning 404 on direct navigation to React routes like /settings, /rules, etc. This controller forwards all non-API, non-static paths to index.html so React Router handles the routing.

Excludes: /api, /ws, /swagger, /v3, /webjars, /static, /assets

[charliecreates]

The SPA forwarding approach is correct in intent, but the current route pattern is brittle: it can miss some SPA routes and can over-exclude legitimate paths (e.g. /apiary/...) due to prefix matching. The mapping also risks forwarding root-level static files (e.g. robots.txt, manifest.webmanifest) to index.html unless you guard against dotted paths. Adjusting the patterns to (1) match both single- and multi-segment routes reliably and (2) exclude file-like paths will make this robust across common Spring routing behaviors.

Summary of changes

What changed

• Added a new Spring MVC controller SpaForwardingController (src/main/java/com/eventara/config/SpaForwardingController.java).
• Introduced a @GetMapping that forwards / and most non-API/non-static paths to forward:/index.html so React Router can handle client-side routing.
• Implemented exclusions via a regex path variable to avoid forwarding requests under api, ws, swagger, v3, webjars, static, assets, and favicon.ico.