refactor(snippets): adopt alias/title model and markdown UX

- rename snippet identity from name to alias and add required title fields

- migrate snippet API, forms, cards, and detail views to alias/title semantics

- render markdown descriptions with short card previews and split vendor chunks

client/src/api/client.ts

@@ -90,7 +90,7 @@ export const snippets = {
   get(id: string): Promise<Snippet> {
     return request(`/snippets/${id}`);
   },
-  create(payload: Pick<Snippet, 'name' | 'code'> & { description?: string }): Promise<Snippet> {
+  create(payload: Pick<Snippet, 'alias' | 'title' | 'code'> & { description?: string }): Promise<Snippet> {
     return request('/snippets', {
       method: 'POST',
       body: JSON.stringify(payload),
@@ -98,7 +98,7 @@ export const snippets = {
   },
   update(
     id: string,
-    patch: Partial<Pick<Snippet, 'name' | 'description' | 'code'>>,
+    patch: Partial<Pick<Snippet, 'alias' | 'title' | 'description' | 'code'>>,
   ): Promise<Snippet> {
     return request(`/snippets/${id}`, {
       method: 'PATCH',