feat: units system — mm/cm/m switchable, configurable grid, real measurements, formatted display

frontend/src/services/api.ts

@@ -608,6 +608,33 @@ export async function deleteGlobalBlock(token: string, id: string): Promise<void
 
 export { API_BASE };
 
+// ─── Settings (Key/Value) ────────────────────────────────
+export interface Setting {
+  key: string;
+  value: string;
+  updated_at: string;
+}
+
+export async function getSetting(token: string, key: string): Promise<Setting | null> {
+  const res = await fetch(`${API_BASE}/api/settings/${encodeURIComponent(key)}`, {
+    method: 'GET',
+    headers: authHeaders(token),
+  });
+  if (res.status === 404) return null;
+  if (!res.ok) throw new Error(`Failed to fetch setting: ${key}`);
+  return res.json();
+}
+
+export async function setSetting(token: string, key: string, value: string): Promise<Setting> {
+  const res = await fetch(`${API_BASE}/api/settings/${encodeURIComponent(key)}`, {
+    method: 'PUT',
+    headers: authHeaders(token),
+    body: JSON.stringify({ value }),
+  });
+  if (!res.ok) throw new Error(`Failed to save setting: ${key}`);
+  return res.json();
+}
+
 // ─── AI Copilot ─────────────────────────────────────────
 export interface AIChatMessage {
   role: string;