fix(admin-tags): name clears after save and wrong confirmation text

SvelteKit's use:enhance resets the form after a successful action.
The name input used value={data.tag.name} without bind:, so Svelte 5's
fine-grained reactivity did not re-apply the unchanged value after the
reset — leaving the field empty. Passing reset: false to update() fixes
this.

Also corrected the confirmation message from "renamed" to "saved" in
all three locales, since the action updates name, parent, and color.

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

frontend/messages/de.json

@@ -180,7 +180,7 @@
 	"admin_tags_empty": "Keine Schlagworte vorhanden.",
 	"admin_tags_select_prompt": "Wähle ein Schlagwort aus der Liste.",
 	"admin_tag_edit_heading": "Schlagwort: {name}",
-	"admin_tag_updated": "Schlagwort umbenannt.",
+	"admin_tag_updated": "Schlagwort gespeichert.",
 	"admin_unsaved_warning": "Du hast ungespeicherte Änderungen – speichere oder verwerfe, bevor du wechselst.",
 	"admin_btn_collapse_list": "Liste einklappen",
 	"admin_btn_expand_list": "Liste ausklappen",