feat: supplier name autocomplete on received invoices

- Added GET /api/admin/received-invoices/suppliers endpoint (distinct names)
- Upload and edit forms use HTML datalist for browser-native autocomplete
- Suggestions loaded once on page mount

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/admin/pages/ReceivedInvoices.tsx

@@ -135,6 +135,9 @@ export default function ReceivedInvoices({ statsMonth, statsYear, uploadOpen, se
   const [deleting, setDeleting] = useState(false)
   const [saving, setSaving] = useState(false)
 
+  // Supplier autocomplete
+  const [supplierNames, setSupplierNames] = useState<string[]>([])
+
   // Upload state
   const [uploadFiles, setUploadFiles] = useState<File[]>([])
   const [uploadMeta, setUploadMeta] = useState<UploadMeta[]>([])
@@ -177,6 +180,14 @@ export default function ReceivedInvoices({ statsMonth, statsYear, uploadOpen, se
 
   useEffect(() => { fetchList() }, [fetchList])
 
+  // Fetch supplier names for autocomplete
+  useEffect(() => {
+    apiFetch(`${API_BASE}/received-invoices/suppliers`)
+      .then(r => r.json())
+      .then(d => { if (d.success) setSupplierNames(d.data || []) })
+      .catch(() => {})
+  }, [])
+
   // Fetch stats (silent refresh without animation)
   const refreshStats = useCallback(async () => {
     try {
@@ -737,9 +748,11 @@ export default function ReceivedInvoices({ statsMonth, statsYear, uploadOpen, se
                       <FormField label="Dodavatel" error={uploadErrors[idx]?.supplier_name} required>
                         <input
                           type="text"
+                          list="supplier-suggestions"
                           className={`admin-form-input${uploadErrors[idx]?.supplier_name ? ' has-error' : ''}`}
                           value={uploadMeta[idx]?.supplier_name || ''}
                           onChange={(e) => updateMeta(idx, 'supplier_name', e.target.value)}
+                          autoComplete="off"
                         />
                       </FormField>
                       <FormField label="Č. faktury">
@@ -860,10 +873,12 @@ export default function ReceivedInvoices({ statsMonth, statsYear, uploadOpen, se
               <FormField label="Dodavatel" required>
                 <input
                   type="text"
+                  list="supplier-suggestions"
                   className="admin-form-input"
                   value={editInvoice.supplier_name}
                   onChange={(e) => setEditInvoice(prev => prev ? { ...prev, supplier_name: e.target.value } : null)}
                   readOnly={ro}
+                  autoComplete="off"
                 />
               </FormField>
               <FormField label="Č. faktury">
@@ -991,6 +1006,12 @@ export default function ReceivedInvoices({ statsMonth, statsYear, uploadOpen, se
         type="danger"
         loading={deleting}
       />
+
+      <datalist id="supplier-suggestions">
+        {supplierNames.map(name => (
+          <option key={name} value={name} />
+        ))}
+      </datalist>
     </>
   )
 }