Add unit API and article unitamount/unitSi patch.

Units use the selected company; article PATCH accepts name/unitamount/unitSi.

src/api/routes/article.js

@@ -36,6 +36,8 @@ function articleErrorStatus(error) {
     if (error.message === 'Article has children') return 400;
     if (error.message === 'Invalid prices') return 400;
     if (error.message === 'POS customer group required') return 400;
+    if (error.message === 'Invalid unitamount') return 400;
+    if (error.message === 'Unit not found') return 404;
     return 500;
 }
 
@@ -185,7 +187,9 @@ export function register(app, basePath = '') {
      *   patch:
      *     tags: [Article]
      *     summary: Update article by SKU
-     *     description: Updates an article name by SKU; returns the same detail shape as GET.
+     *     description: |
+     *       Patches article fields. At least one of `name`, `unitamount`, `unitSi` required.
+     *       `unitSi` must already exist for the company. Returns the same detail shape as GET.
      *     security:
      *       - cookieAuth: []
      *     x-markdown: article/update.md
@@ -202,12 +206,18 @@ export function register(app, basePath = '') {
      *         application/json:
      *           schema:
      *             type: object
-     *             required: [name]
      *             properties:
      *               name:
      *                 type: string
+     *               unitamount:
+     *                 type: number
+     *                 description: Must be finite and `> 0`
+     *               unitSi:
+     *                 type: string
+     *                 description: Existing company unit `si`
      *             example:
-     *               name: Updated name
+     *               unitamount: 0.24
+     *               unitSi: l
      *     responses:
      *       200:
      *         description: Updated article detail
@@ -219,7 +229,7 @@ export function register(app, basePath = '') {
      *                 article:
      *                   $ref: '#/components/schemas/ArticleDetail'
      *       400:
-     *         description: Validation error
+     *         description: Validation error (Name required / Invalid unitamount)
      *         content:
      *           application/json:
      *             schema:
@@ -237,7 +247,7 @@ export function register(app, basePath = '') {
      *             schema:
      *               $ref: '#/components/schemas/Error'
      *       404:
-     *         description: Article not found
+     *         description: Article or unit not found
      *         content:
      *           application/json:
      *             schema:
@@ -309,13 +319,24 @@ export function register(app, basePath = '') {
             return res.status(400).json({ error: 'sku is required' });
         }
 
-        const name = typeof req.body?.name === 'string' ? req.body.name.trim() : '';
-        if (!name) {
-            return res.status(400).json({ error: 'name is required' });
+        const body = req.body ?? {};
+        const patch = {};
+        if (Object.prototype.hasOwnProperty.call(body, 'name')) {
+            patch.name = body.name;
+        }
+        if (Object.prototype.hasOwnProperty.call(body, 'unitamount')) {
+            patch.unitamount = body.unitamount;
+        }
+        if (Object.prototype.hasOwnProperty.call(body, 'unitSi')) {
+            patch.unitSi = body.unitSi;
+        }
+
+        if (!('name' in patch) && !('unitamount' in patch) && !('unitSi' in patch)) {
+            return res.status(400).json({ error: 'name, unitamount, or unitSi is required' });
         }
 
         try {
-            const article = await db.updateBySku(req.user.id, decodeURIComponent(sku), { name });
+            const article = await db.updateBySku(req.user.id, decodeURIComponent(sku), patch);
             res.status(200).json({ article });
         } catch (error) {
             const status = articleErrorStatus(error);