fix(recipe): Favoriten-Markierung persistiert beim Neuladen

Bug: Beim Neuanzeigen einer Rezeptseite war der Favoriten-Button immer
grau — isFav wurde als local $state(false) initialisiert und die
checkFavorite()-Funktion war eine Stub-Implementation, die nichts
gemacht hat. State lebte nur innerhalb einer Session.

Fix:
- Neue Server-Funktion listFavoriteProfiles(db, recipeId): number[]
  in $lib/server/recipes/actions.ts
- +page.server.ts lädt favorite_profile_ids mit in die Page-Daten
- +page.svelte macht isFav zum $derived aus favoriteProfileIds +
  aktivem Profil. toggleFavorite mutiert die lokale Liste (Add/Remove
  der aktiven Profil-ID) — beim nächsten Load ist die Server-Liste
  wieder Source of Truth.
- Alte Stub-Funktion checkFavorite() entfernt (inkl. Aufruf in
  onMount).

src/lib/server/recipes/actions.ts

@@ -73,6 +73,17 @@ export function isFavorite(
   );
 }
 
+export function listFavoriteProfiles(
+  db: Database.Database,
+  recipeId: number
+): number[] {
+  return (
+    db
+      .prepare('SELECT profile_id FROM favorite WHERE recipe_id = ?')
+      .all(recipeId) as { profile_id: number }[]
+  ).map((r) => r.profile_id);
+}
+
 export function logCooked(
   db: Database.Database,
   recipeId: number,

src/routes/recipes/[id]/+page.server.ts

@@ -5,6 +5,7 @@ import { getRecipeById } from '$lib/server/recipes/repository';
 import {
   listComments,
   listCookingLog,
+  listFavoriteProfiles,
   listRatings
 } from '$lib/server/recipes/actions';
 
@@ -17,7 +18,8 @@ export const load: PageServerLoad = async ({ params }) => {
   const ratings = listRatings(db, id);
   const comments = listComments(db, id);
   const cooking_log = listCookingLog(db, id);
+  const favorite_profile_ids = listFavoriteProfiles(db, id);
   const avg_stars =
     ratings.length === 0 ? null : ratings.reduce((s, r) => s + r.stars, 0) / ratings.length;
-  return { recipe, ratings, comments, cooking_log, avg_stars };
+  return { recipe, ratings, comments, cooking_log, favorite_profile_ids, avg_stars };
 };

src/routes/recipes/[id]/+page.svelte

@@ -13,7 +13,7 @@
   let ratings = $state<typeof data.ratings>([]);
   let comments = $state<CommentRow[]>([]);
   let cookingLog = $state<typeof data.cooking_log>([]);
-  let isFav = $state(false);
+  let favoriteProfileIds = $state<number[]>([]);
   let onWishlist = $state(false);
   let newComment = $state('');
 
@@ -21,6 +21,7 @@
     ratings = [...data.ratings];
     comments = [...data.comments];
     cookingLog = [...data.cooking_log];
+    favoriteProfileIds = [...data.favorite_profile_ids];
   });
 
   const myRating = $derived(
@@ -29,14 +30,9 @@
       : null
   );
 
-  async function checkFavorite() {
-    if (!profileStore.active) {
-      isFav = false;
-      return;
-    }
-    // Fetch favorite status via list endpoint (quick hack: GET not implemented, infer from no-op)
-    // Not critical for MVP — we mutate state on toggle.
-  }
+  const isFav = $derived(
+    profileStore.active ? favoriteProfileIds.includes(profileStore.active.id) : false
+  );
 
   async function setRating(stars: number) {
     if (!profileStore.active) {
@@ -64,13 +60,16 @@
       });
       return;
     }
+    const profileId = profileStore.active.id;
     const method = isFav ? 'DELETE' : 'PUT';
     await fetch(`/api/recipes/${data.recipe.id}/favorite`, {
       method,
       headers: { 'content-type': 'application/json' },
-      body: JSON.stringify({ profile_id: profileStore.active.id })
+      body: JSON.stringify({ profile_id: profileId })
     });
-    isFav = !isFav;
+    favoriteProfileIds = isFav
+      ? favoriteProfileIds.filter((id) => id !== profileId)
+      : [...favoriteProfileIds, profileId];
   }
 
   async function logCooked() {
@@ -183,7 +182,6 @@
 
   onMount(() => {
     void requestWakeLock();
-    void checkFavorite();
     void refreshWishlistState();
     const onVisibility = () => {
       if (document.visibilityState === 'visible' && !wakeLock) void requestWakeLock();