feat(odin): personalized greeting hero on the new-conversation screen

Time-based Czech greeting + the user's first name (e.g. "Dobrý večer, Admin")
above the big gradient "Odin" wordmark, with a stylish description line. Drop
the redundant mark from the hero (it lives on the nav item + thinking state).

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

src/admin/components/odin/OdinChat.tsx

@@ -62,10 +62,26 @@ function summaryNote(reviews: ReviewInvoice[]): string {
 export default function OdinChat() {
   const alert = useAlert();
   const qc = useQueryClient();
-  const { hasPermission } = useAuth();
+  const { user, 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");
+  // Time-based Czech greeting + the user's first name (client-local time).
+  const greeting = (() => {
+    const h = new Date().getHours();
+    const part =
+      h < 9
+        ? "Dobré ráno"
+        : h < 12
+          ? "Dobrý den"
+          : h < 18
+            ? "Dobré odpoledne"
+            : "Dobrý večer";
+    const name = (user?.fullName || user?.username || "")
+      .trim()
+      .split(/\s+/)[0];
+    return name ? `${part}, ${name}` : part;
+  })();
   const { data: usage } = useQuery(aiUsageOptions());
   const { data: convData, isPending: convPending } = useQuery(
     aiConversationsOptions(),
@@ -425,6 +441,7 @@ export default function OdinChat() {
           turns={turns}
           busy={busy}
           loading={messagesLoading}
+          greeting={greeting}
           threadRef={threadRef}
         />