feat(ares): ARES company lookup with prefill in customer/supplier modals

New /api/admin/ares proxy (browser cannot reach ares.gov.cz - CORS+CSP):
GET /ico/:ico and GET /search?q= map the MFCR REST API to the form
shape (street incl. orientation numbers, "511 01" PSC format, DIC).
Guarded by customers.create/edit + warehouse.manage; token errors map
to Czech messages. Shared AresAdornment button sits in the Nazev and
ICO fields of both modals: ICO mode fills directly, name mode searches
with a result picker. Tested against live ARES (BOHA, ICO 22599851).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/admin/pages/OffersCustomers.tsx

@@ -12,6 +12,7 @@ import {
   type CustomField,
 } from "../lib/queries/offers";
 import { useApiMutation } from "../lib/queries/mutations";
+import AresAdornment, { type AresCompany } from "../components/AresLookup";
 import {
   Button,
   Card,
@@ -267,6 +268,21 @@ export default function OffersCustomers() {
     return key;
   };
 
+  // ARES prefill — overwrite the company fields with registry data (the
+  // button is an explicit user action, so overwriting is the expected UX).
+  const fillFromAres = (c: AresCompany) => {
+    setForm((prev) => ({
+      ...prev,
+      name: c.name || prev.name,
+      street: c.street,
+      city: c.city,
+      postal_code: c.postal_code,
+      country: c.country,
+      company_id: c.ico,
+      vat_id: c.dic || "",
+    }));
+  };
+
   const openCreateModal = () => {
     setEditingCustomer(null);
     setForm({
@@ -535,6 +551,15 @@ export default function OffersCustomers() {
               setForm((prev) => ({ ...prev, name: e.target.value }))
             }
             placeholder="Název firmy / jméno"
+            InputProps={{
+              endAdornment: (
+                <AresAdornment
+                  mode="name"
+                  query={form.name}
+                  onFill={fillFromAres}
+                />
+              ),
+            }}
           />
         </Field>
         <Field label="Ulice">
@@ -596,6 +621,15 @@ export default function OffersCustomers() {
                   company_id: e.target.value,
                 }))
               }
+              InputProps={{
+                endAdornment: (
+                  <AresAdornment
+                    mode="ico"
+                    query={form.company_id}
+                    onFill={fillFromAres}
+                  />
+                ),
+              }}
             />
           </Field>
           <Field label="DIČ">