🌐 fix(i18n): start adding translations for timeline events (#4497)

- Fixed hardcoded Recipe Created message in timeline events
- Added initial recipe-created translations:
  - de-DE: Rezept erstellt
  - en-US: Recipe created

Part of #4497

mealie/lang/messages/de-DE.json

@@ -4,6 +4,7 @@
     },
     "recipe": {
         "unique-name-error": "Rezeptnamen müssen einzigartig sein",
+        "recipe-created": "Rezept erstellt",
         "recipe-defaults": {
             "ingredient-note": "250 g Mehl",
             "step-text": "Zubereitungs-Schritte und andere Felder der Rezeptseite unterstützen Markdown Syntax.\n\n**Füge einen Link hinzu**\n\n[Mein Link](https://demo.mealie.io)\n"

mealie/lang/messages/en-US.json

@@ -4,6 +4,7 @@
     },
     "recipe": {
         "unique-name-error": "Recipe names must be unique",
+        "recipe-created": "Recipe created",
         "recipe-defaults": {
             "ingredient-note": "1 Cup Flour",
             "step-text": "Recipe steps as well as other fields in the recipe page support markdown syntax.\n\n**Add a link**\n\n[My Link](https://demo.mealie.io)\n"

mealie/services/recipe/recipe_service.py

@@ -190,7 +190,7 @@ def create_one(self, create_data: Recipe | CreateRecipe) -> Recipe:
         timeline_event_data = RecipeTimelineEventCreate(
             user_id=new_recipe.user_id,
             recipe_id=new_recipe.id,
-            subject="Recipe Created",
+            subject=self.t("recipe.recipe-created"),
             event_type=TimelineEventType.system,
             timestamp=new_recipe.created_at or datetime.now(timezone.utc),
         )