Add unit API and article unitamount/unitSi patch.

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

docs/api/routes/unit/list.md

@@ -0,0 +1,30 @@
+# `GET /unit`
+
+Protected. Requires a valid session cookie (`credentials: 'include'`).
+
+List units
+
+Lists units for the authenticated user's selected company (default-language symbol/name).
+
+## Response `200`
+
+Unit list
+
+```json
+{
+  "units": []
+}
+```
+
+## Errors
+
+| Status | Description |
+|--------|-------------|
+| 400 | No company selected — `{"error":"…"}` |
+| 401 | Unauthorized — `{"error":"…"}` |
+| 403 | Not authorized — `{"error":"…"}` |
+| 404 | Company not found — `{"error":"…"}` |
+
+---
+
+_Generated from `@openapi` JSDoc. Do not edit by hand — run `npm run docs:api`._