refactor(calculate-version): 將版本計算邏輯由 bash 改寫為 Node.js 並依功能分檔

保留 entrypoint.sh 作為容器進入點，改為啟動 app/ 下的 Node.js 程式；
依功能拆分為 logger/config/version/releases/output/index，並更新 Dockerfile 改用 node:lts-alpine。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/test/output.test.js

@@ -0,0 +1,35 @@
+'use strict';
+
+const { test, beforeEach, afterEach } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const os = require('node:os');
+const path = require('node:path');
+const { writeOutput } = require('../output');
+
+let workspace;
+
+beforeEach(() => {
+    workspace = fs.mkdtempSync(path.join(os.tmpdir(), 'calc-version-'));
+});
+
+afterEach(() => {
+    fs.rmSync(workspace, { recursive: true, force: true });
+});
+
+test('writeOutput 將 name=value 附加寫入輸出檔', () => {
+    const file = path.join(workspace, 'output');
+    writeOutput('version', '1.2.3', file);
+    assert.equal(fs.readFileSync(file, 'utf8'), 'version=1.2.3\n');
+});
+
+test('writeOutput 以附加方式保留既有內容', () => {
+    const file = path.join(workspace, 'output');
+    fs.writeFileSync(file, 'existing=1\n');
+    writeOutput('version', '1.2.3', file);
+    assert.equal(fs.readFileSync(file, 'utf8'), 'existing=1\nversion=1.2.3\n');
+});
+
+test('writeOutput 在未提供輸出檔時丟出錯誤', () => {
+    assert.throws(() => writeOutput('version', '1.2.3', undefined), /GITHUB_OUTPUT 未設定/);
+});