Allow non-admin users to access dashboard

- Change dashboard route from adminGet to authed middleware
- Show account counts and audit events only for admin users
- Show welcome message for non-admin authenticated users

Security: non-admin users cannot access account lists or audit
events; admin-only data is gated by claims.HasRole("admin") in
the handler, not just at the route level.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/ui/ui.go

@@ -314,7 +314,7 @@ func (u *UIServer) Register(mux *http.ServeMux) {
 		return authed(u.requireAdminRole(http.HandlerFunc(h)))
 	}
 
-	uiMux.Handle("GET /dashboard", adminGet(u.handleDashboard))
+	uiMux.Handle("GET /dashboard", authed(http.HandlerFunc(u.handleDashboard)))
 	uiMux.Handle("GET /accounts", adminGet(u.handleAccountsList))
 	uiMux.Handle("POST /accounts", admin(u.handleCreateAccount))
 	uiMux.Handle("GET /accounts/{id}", adminGet(u.handleAccountDetail))
@@ -609,6 +609,7 @@ type LoginData struct {
 // DashboardData is the view model for the dashboard page.
 type DashboardData struct {
 	PageData
+	IsAdmin        bool
 	RecentEvents   []*db.AuditEventView
 	TotalAccounts  int
 	ActiveAccounts int