fix(frontend): submit-time data flow (rating scale, table reactivity)

- rating submitted doubled: the * 2 belonged to the retired 0-5
  slider scale while StarInput already works in backend 0-10 units,
  so every rating arrived doubled (9 became 18, both backends
  rejected it); form value now passes through unscaled, display and
  words map already native 0-10
- StarInput gains an optional name prop rendering a hidden input,
  restoring the rating form field the old slider exposed; Rating
  passes name="rating"
- table updates go immutable (new array every path): in-place
  mutation with the same reference never reliably invalidated the
  Svelte 5 $derived, which left the grid stale after successful
  submits; replace-or-append semantics unchanged
- per-page dropdown reads the event value synchronously (Svelte 5
  nulls currentTarget after dispatch, crashing the old
  read-inside-.then)
- detail poster column shares a flex centering context so poster and
  stars align by construction at every width

frontend/src/helperComponents/Anime.svelte

@@ -169,7 +169,9 @@
     for (let field of formData) {
       const [key, value] = field;
       if (key === "rating") {
-        submitData.rating = Number(value) * 2;
+        // Form value is already 0-10 (StarInput works in backend units).
+        // The old * 2 belonged to the retired 0-5 slider scale.
+        submitData.rating = Number(value);
         continue;
       }
       if (key === "episodes") {

frontend/src/helperComponents/Pagination.svelte

@@ -43,14 +43,14 @@
   function changeCountPerPage(
     e: Event & { currentTarget: HTMLSelectElement },
   ): void {
-    App.GetAniListUserWatchingList(1, Number(e.currentTarget.value), sort).then(
-      (result) => {
-        animePerPage.set(Number(e.currentTarget.value));
-        watchListPage.set(1);
-        aniListWatchlist.set(result);
-        aniListLoggedIn.set(true);
-      },
-    );
+    // Read synchronously: Svelte 5 nulls currentTarget after dispatch.
+    const count = Number(e.currentTarget.value);
+    App.GetAniListUserWatchingList(1, count, sort).then((result) => {
+      animePerPage.set(count);
+      watchListPage.set(1);
+      aniListWatchlist.set(result);
+      aniListLoggedIn.set(true);
+    });
   }
 </script>
 

frontend/src/helperComponents/Rating.svelte

@@ -19,7 +19,7 @@
 </script>
 
 <div>
-    <StarInput bind:value={score} min={0} max={10} step={1} />
+    <StarInput bind:value={score} min={0} max={10} step={1} name="rating" />
     <p>Rating:  {score}</p>
     <p>{ratingInWords[score]}</p>
 </div>