style: replaced hardcoded links to references to AppPath (#5968)

# Motivation

We have hardcoded links in two components: `LinkToSettings` and
`LinkToReporting`. We can replace these with references to the `AppPath`
object, which exports all the routes.

# Changes

- Replace hardcoded values with references to `AppPath`.

# Tests

- Not necessary

# Todos

- [ ] Add entry to changelog (if necessary).
Not necessary

frontend/src/lib/components/header/LinkToReporting.svelte

@@ -1,11 +1,12 @@
 <script lang="ts">
   import { beforeNavigate } from "$app/navigation";
+  import { AppPath } from "$lib/constants/routes.constants";
   import { i18n } from "$lib/stores/i18n";
   import { IconDocument } from "@dfinity/gix-components";
   import { createEventDispatcher } from "svelte";
 
   const dispatcher = createEventDispatcher();
-  const linkToReporting = "/reporting";
+  const linkToReporting = AppPath.Reporting;
 
   beforeNavigate(() => dispatcher("nnsLink"));
 </script>

frontend/src/lib/components/header/LinkToSettings.svelte

@@ -1,11 +1,12 @@
 <script lang="ts">
   import { beforeNavigate } from "$app/navigation";
+  import { AppPath } from "$lib/constants/routes.constants";
   import { i18n } from "$lib/stores/i18n";
   import { IconSettings } from "@dfinity/gix-components";
   import { createEventDispatcher } from "svelte";
 
   const dispatcher = createEventDispatcher();
-  const linkToSettings = "/settings";
+  const linkToSettings = AppPath.Settings;
 
   beforeNavigate(() => dispatcher("nnsLink"));
 </script>