feat: simplify RBAC roles and remove dev role switcher

- Simplified RBAC system to two roles: super_admin and user.
- Removed tenant_admin and rp_admin roles across backend and frontend.
- Removed Dev Role Switcher feature from adminfront.
- Updated all handlers, middlewares, and navigation to reflect the new role model.
- Fixed backend build errors and updated tests.

backend/internal/handler/admin_handler_test.go

@@ -155,7 +155,7 @@ func TestAdminHandler_UserProjectionStatusRequiresSuperAdmin(t *testing.T) {
 	}
 	app := fiber.New()
 	app.Use(func(c *fiber.Ctx) error {
-		c.Locals("user_profile", &domain.UserProfileResponse{ID: "tenant-admin", Role: domain.RoleTenantAdmin})
+		c.Locals("user_profile", &domain.UserProfileResponse{ID: "tenant-admin", Role: "tenant_admin"})
 		return c.Next()
 	})
 	app.Get("/api/v1/admin/projections/users", h.GetUserProjectionStatus)
@@ -245,7 +245,7 @@ func TestAdminHandler_GetRPUsageDailyChecksTenantPermission(t *testing.T) {
 	app.Use(func(c *fiber.Ctx) error {
 		c.Locals("user_profile", &domain.UserProfileResponse{
 			ID:   "user-1",
-			Role: domain.RoleTenantAdmin,
+			Role: "tenant_admin",
 		})
 		return c.Next()
 	})