AIタスク管理プロジェクトのドキュメントとサンプルコードを追加

docs/3-web-servers/14-project/_samples/ai-todo/.gitignore

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+node_modules/
+generated/
+.env

docs/3-web-servers/14-project/_samples/ai-todo/main.mjs

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+import express from "express";
+import { PrismaClient } from "./generated/prisma/index.js";
+
+const app = express();
+const client = new PrismaClient();
+
+app.use(express.json());
+app.use(express.static("./public"));
+
+app.get("/todos", async (request, response) => {
+  const todos = await client.todo.findMany({ orderBy: { id: "asc" } });
+  response.json(todos);
+});
+
+app.post("/todos", async (request, response) => {
+  const todo = await client.todo.create({
+    data: {
+      title: request.body.title,
+      dueAt: new Date(request.body.dueAt),
+    },
+  });
+  response.json(todo);
+});
+
+app.delete("/todos/:id", async (request, response) => {
+  await client.todo.delete({
+    where: { id: parseInt(request.params.id) },
+  });
+  response.json({ success: true });
+});
+
+app.post("/todos/ai", async (request, response) => {
+  const systemPrompt = `
+ユーザーの入力から、ToDoのタイトルと期限を抽出してください。
+1行目にタイトル、2行目に期限（ISO8601形式、タイムゾーンは東京）を出力してください。
+現在日時: ${new Date().toISOString()}
+
+例
+現在日時: 2026-01-20T12:00:00+09:00
+入力: 明日の10時に会議
+出力: 会議
+2026-01-21T10:00:00+09:00
+`;
+
+  const result = await fetch("https://openrouter.ai/api/v1/chat/completions", {
+    method: "POST",
+    headers: {
+      Authorization: `Bearer ${process.env.OPENROUTER_API_KEY}`,
+      "Content-Type": "application/json",
+    },
+    body: JSON.stringify({
+      model: "openrouter/free",
+      messages: [
+        { role: "system", content: systemPrompt },
+        { role: "user", content: request.body.instruction },
+      ],
+    }),
+  });
+  const data = await result.json();
+  const content = data.choices[0].message.content;
+  const lines = content.split("\n");
+  const todo = await client.todo.create({
+    data: { title: lines[0], dueAt: new Date(lines[1]) },
+  });
+  response.json(todo);
+});
+
+app.listen(3000);