feat(api): add public business info route and TotalVATCollected to daily summary

Expose GET /business-info public endpoint for non-admin users. Add TotalVATCollected field to DailySummary and compute it in the aggregate query.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/main.go

@@ -207,6 +207,9 @@ func main() {
 		// Public contact info
 		r.Get("/contact", user.GetContactInfoHandler)
 
+		// Public business info (limited, safe for non-admin users)
+		r.Get("/business-info", admin.GetPublicBusinessInfo)
+
 		// Portfolio
 		r.Route("/portfolio", func(r chi.Router) {
 			r.Get("/images", portfolio.ListImages)