feat(dashboard): new layout with sync button and top 5 most played

Remove the placeholder tiles and the settings tile, fix the mobile header width. iconUrl/formatPlaytime move to utils/games.js (599 min now shows 10h, not 10.0h), and the sync button logic to the useForceSync hook shared with the library.

src/hooks/useForceSync.js

@@ -0,0 +1,50 @@
+import {useState} from 'react';
+import {useNavigate} from 'react-router-dom';
+import {useTranslation} from 'react-i18next';
+
+const RELOAD_DELAY_MS = 4000;
+
+/**
+ * Starts a library sync (POST /api/library/sync) and calls onStarted after a short delay,
+ * so the caller can reload once Steam data has arrived.
+ */
+export default function useForceSync(onStarted) {
+    const {t} = useTranslation();
+    const navigate = useNavigate();
+    const [busy, setBusy] = useState(false);
+    const [message, setMessage] = useState(null);
+
+    const trigger = async () => {
+        const token = localStorage.getItem('tbp_jwt');
+        if (!token) {
+            navigate('/login');
+            return;
+        }
+        setBusy(true);
+        setMessage(null);
+        try {
+            const response = await fetch(`${import.meta.env.VITE_CORE_API_URL}/api/library/sync`, {
+                method: 'POST',
+                headers: {'Authorization': `Bearer ${token}`},
+            });
+            if (response.status === 429) {
+                const json = await response.json().catch(() => ({}));
+                setMessage(t('LIBRARY.SYNC_COOLDOWN', {seconds: json.retryAfterSeconds ?? 60}));
+                return;
+            }
+            if (!response.ok) {
+                setMessage(t('LIBRARY.SYNC_FAILED'));
+                return;
+            }
+            setMessage(t('LIBRARY.SYNC_STARTED'));
+            setTimeout(onStarted, RELOAD_DELAY_MS);
+        } catch (err) {
+            console.error('sync trigger error:', err);
+            setMessage(t('INFO.ERROR.NETWORK_FAILURE'));
+        } finally {
+            setBusy(false);
+        }
+    };
+
+    return {trigger, busy, message};
+}