fix(odin): gate Uložit on invoices.create + correct invoice invalidation key

Final review caught two minor issues:
- saveInvoice invalidated ["received-invoices"], which matches no query (the
  received list/stats are keyed ["invoices","received",…]); use ["invoices"]
  so the list/stats actually refresh after an import.
- The Save button hit /received-invoices (requires invoices.create) while Odin
  is gated only on ai.use; disable Uložit (with a hint) when the user lacks
  invoices.create so the UI never offers a 403 action. Dormant today (ai.use is
  admin-only and admin bypasses checks) but correct going forward.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/components/odin/OdinChat.tsx

@@ -4,6 +4,7 @@ import Box from "@mui/material/Box";
 import Typography from "@mui/material/Typography";
 import apiFetch from "../../utils/api";
 import { useAlert } from "../../context/AlertContext";
+import { useAuth } from "../../context/AuthContext";
 import {
   aiUsageOptions,
   aiConversationsOptions,
@@ -61,6 +62,10 @@ function summaryNote(reviews: ReviewInvoice[]): string {
 export default function OdinChat() {
   const alert = useAlert();
   const qc = useQueryClient();
+  const { hasPermission } = useAuth();
+  // Saving an extracted invoice hits /received-invoices (needs invoices.create);
+  // Odin itself only needs ai.use, so the Save affordance is gated separately.
+  const canSave = hasPermission("invoices.create");
   const { data: usage } = useQuery(aiUsageOptions());
   const { data: convData, isPending: convPending } = useQuery(
     aiConversationsOptions(),
@@ -304,7 +309,7 @@ export default function OdinChat() {
       if (!res.ok) throw new Error(body?.error || "Uložení selhalo");
       alert.success("Faktura uložena");
       setReview((r) => r.filter((x) => x.uid !== inv.uid));
-      qc.invalidateQueries({ queryKey: ["received-invoices"] });
+      qc.invalidateQueries({ queryKey: ["invoices"] });
     } catch (e) {
       alert.error(e instanceof Error ? e.message : "Uložení selhalo");
     } finally {
@@ -445,6 +450,7 @@ export default function OdinChat() {
               key={inv.uid}
               inv={inv}
               busy={busy}
+              canSave={canSave}
               onChange={patch}
               onSave={saveInvoice}
               onDiscard={(uid) =>