fix(detail): resync reaction toggle across manga navigation

The detail page component is reused across /manga/A -> /manga/B
navigations (clicking a similar or recommendation card), so
ReactionButtons' locally-held `current` state kept the previous manga's
reaction until interacted with — a visibly wrong thumb on the new page.
Re-seed `current` from the loader-supplied prop via an effect keyed on
mangaId. Also fetch the homepage's two independent /me/* shelves
concurrently (Promise.allSettled) instead of in series.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/routes/+page.svelte

@@ -311,24 +311,24 @@
         }
         await hydrateFromUrl();
         await load();
-        // Fetch the "Continue reading" shelf after the catalogue so the
-        // public browse path stays unauthenticated and unblocked. Returns
-        // empty for guests (401 swallowed), which hides the shelf.
-        try {
-            const progress = await listMyReadProgressOrEmpty();
+        // Fetch the personal shelves after the catalogue so the public browse
+        // path stays unauthenticated and unblocked. Both are independent
+        // `/me/*` calls, so fire them concurrently rather than in series.
+        // Each is isolated: a failure (or 401 for guests) hides its own shelf
+        // without touching the catalogue or the other shelf.
+        const [progressResult, recsResult] = await Promise.allSettled([
+            listMyReadProgressOrEmpty(),
+            listMyRecommendations()
+        ]);
+        if (progressResult.status === 'fulfilled') {
             // Drop finished series (read to the end, nothing new) — a
             // "Continue reading" shelf is for what's still in progress.
-            continueEntries = progress.items.filter((e) => !isCaughtUp(e));
-        } catch {
-            // Never let a history hiccup break the catalogue — leave the
-            // shelf hidden.
+            continueEntries = progressResult.value.items.filter((e) => !isCaughtUp(e));
         }
-        try {
+        if (recsResult.status === 'fulfilled') {
             // Personal "Recommended for you" feed (empty for guests / no
             // taste signals yet → shelf hidden).
-            recommendations = await listMyRecommendations();
-        } catch {
-            // Non-critical — leave the shelf hidden on failure.
+            recommendations = recsResult.value;
         }
     });