web: move all strings to i18n & improve a11y

- omnibox is now fully usable with a screen reader
- back button is now interpreted as such
- subtext now accepts line breaks

web/src/components/save/buttons/ClearButton.svelte

@@ -1,9 +1,11 @@
 <script>
-    export let click;
+    import { t } from "$lib/i18n/translations";
     import IconX from '@tabler/icons-svelte/IconX.svelte';
+
+    export let click;
 </script>
 
-<button id="clear-button" on:click={click}>
+<button id="clear-button" on:click={click} aria-label={$t("a11y.save.clearInput")}>
     <IconX color="var(--secondary)" size="16px"/>
 </button>