feat(themes): 테마 인덱스/상세 (11 카테고리 · 111 종목)

- seed/themes.py: 반도체/2차전지/바이오/게임/엔터/자동차/금융/조선·방산/플랫폼·AI/유통·소비재/에너지 정적 매핑
- /api/themes (인덱스) + /api/themes/{slug} (종목 카드 + 최신 종가/등락)
- 홈에 ThemeTiles 그리드, /themes/{slug} 상세 페이지

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/lib/api.ts

@@ -186,6 +186,25 @@ export type RelatedResponse = {
   items: Mover[];
 };
 
+export type ThemeIndex = {
+  slug: string;
+  name: string;
+  description: string;
+  code_count: number;
+};
+
+export type ThemesIndexResponse = {
+  items: ThemeIndex[];
+  total: number;
+};
+
+export type ThemeDetailResponse = {
+  slug: string;
+  name: string;
+  description: string;
+  items: Mover[];
+};
+
 async function getJson<T>(path: string, init?: RequestInit): Promise<T> {
   const res = await fetch(`${API_BASE}${path}`, {
     ...init,
@@ -239,4 +258,9 @@ export const api = {
     getJson<RelatedResponse>(
       `/api/markets/related/${encodeURIComponent(code)}?limit=${limit}`,
     ),
+  themesIndex: () => getJson<ThemesIndexResponse>(`/api/themes`),
+  themeDetail: (slug: string, limit = 30) =>
+    getJson<ThemeDetailResponse>(
+      `/api/themes/${encodeURIComponent(slug)}?limit=${limit}`,
+    ),
 };