Remove dead code identified by deadcode tool (#37271)

Ran [`deadcode`](https://pkg.go.dev/golang.org/x/tools/cmd/deadcode)
(`-test ./...`) to find functions, methods and error types unreachable
from any call path (including tests), and removed the truly-dead ones.

Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>

routers/web/home.go

@@ -109,9 +109,3 @@ func HomeSitemap(ctx *context.Context) {
 		log.Error("Failed writing sitemap: %v", err)
 	}
 }
-
-// NotFound render 404 page
-func NotFound(ctx *context.Context) {
-	ctx.Data["Title"] = "Page Not Found"
-	ctx.NotFound(nil)
-}