feat(insta): Trends tab — account focus + external trends + impact preview

- api.js: add getInstaTrends, instaCollectTrends, getInstaPreferences, putInstaPreferences helpers
- InstaCards.jsx: add Cards/Trends tab bar with URL sync (?tab=trends); add AccountFocusPanel (category weight sliders + save), ExternalTrendsPanel (Naver+Google trend rows + manual collect), PreferenceImpactPanel (next extract preview); existing 5-panel Cards tab preserved intact
- InstaCards.css: add ic-tabbar, ic-tab, ic-trends-grid, ic-panel base, ic-focus/ic-trend/ic-impact component styles

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

src/api.js

@@ -544,6 +544,27 @@ export function putInstaPrompt(name, template, description = '') {
   return apiPut(`/api/insta/templates/prompts/${encodeURIComponent(name)}`, { template, description });
 }
 
+// ── insta-lab trends ──
+export function getInstaTrends({ source, category, days = 1 } = {}) {
+  const q = new URLSearchParams();
+  if (source) q.set('source', source);
+  if (category) q.set('category', category);
+  q.set('days', String(days));
+  return apiGet(`/api/insta/trends?${q.toString()}`);
+}
+
+export function instaCollectTrends(categories) {
+  return apiPost('/api/insta/trends/collect', categories ? { categories } : {});
+}
+
+export function getInstaPreferences() {
+  return apiGet('/api/insta/preferences');
+}
+
+export function putInstaPreferences(categories) {
+  return apiPut('/api/insta/preferences', { categories });
+}
+
 // ── Agent Office ──────────────────────────────────
 export const getAgents         = ()           => apiGet('/api/agent-office/agents');
 export const getAgentDetail    = (id)         => apiGet(`/api/agent-office/agents/${id}`);