Add movie collection API and frontend

Express app with an in-memory array as the store (no database) and three
endpoints:

- GET  /api/movies      -> the whole collection
- GET  /api/movies/:id  -> one movie, 404 when the id is unknown
- POST /api/movies      -> add a movie, id assigned by the server

zod schemas are the single source of truth for validation, so a missing
title, genre or year comes back as a 400 with one message per field.
index.html is served by the same app and drives all three endpoints with
fetch(), refreshing the list after a movie is added.

.gitignore

@@ -0,0 +1,28 @@
+# dev
+.yarn/
+!.yarn/releases
+.vscode/*
+!.vscode/launch.json
+!.vscode/*.code-snippets
+.idea/workspace.xml
+.idea/usage.statistics.xml
+.idea/shelf
+
+# deps
+node_modules/
+
+# env
+.env
+.env.production
+
+# logs
+logs/
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+# misc
+.DS_Store