feat: personalized feed — fetch /feed/media when API key is set

If API key present, GET /feed/media from Brain API to collect user's
custom sources, then POST to Feed API with customFeeds array.
Falls back to default GET if no key or fetch fails.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

index.html

@@ -950,7 +950,38 @@ async function loadFeed() {
     document.getElementById('briefList').innerHTML     = '';
 
     try {
-        const res = await fetch(FEED_API, { cache: 'no-store' });
+        const apiKey = localStorage.getItem('posimai-brief-apikey');
+        let res;
+        if (apiKey) {
+            let customFeeds = [];
+            try {
+                const mediaRes = await fetch(API_BASE + '/feed/media', {
+                    headers: { 'Authorization': `Bearer ${apiKey}` }
+                });
+                if (mediaRes.ok) {
+                    const medias = await mediaRes.json();
+                    customFeeds = medias
+                        .filter(m => m.is_active !== false)
+                        .map(m => ({
+                            id: `db-${m.id}`,
+                            name: m.name,
+                            url: m.feed_url,
+                            siteUrl: m.site_url,
+                            category: m.category || 'tech',
+                            icon: 'rss',
+                            dbId: m.id,
+                        }));
+                }
+            } catch (_) { /* カスタムソース取得失敗 → デフォルトのみで続行 */ }
+            res = await fetch(FEED_API, {
+                method: 'POST',
+                cache: 'no-store',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ customFeeds }),
+            });
+        } else {
+            res = await fetch(FEED_API, { cache: 'no-store' });
+        }
         if (!res.ok) throw new Error(`Feed ${res.status}`);
         const data = await res.json();
         const list = (data.articles || []).slice(0, 8);