feat(odin): sidebar brand is a big gradient "Odin" wordmark (drop the icon)

The mark already lives on the nav menu item; the conversation sidebar's brand
no longer duplicates it — just a larger gradient "Odin" wordmark above the new
chat button.

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

src/admin/components/odin/OdinSidebar.tsx

@@ -5,7 +5,6 @@ import Menu from "@mui/material/Menu";
 import MenuItem from "@mui/material/MenuItem";
 import IconButton from "@mui/material/IconButton";
 import { Button, TextField, Modal, ConfirmDialog } from "../../ui";
-import OdinMark from "./OdinMark";
 
 interface OdinSidebarProps {
   conversations: { id: number; title: string }[];
@@ -78,11 +77,21 @@ export default function OdinSidebar({
     >
       {/* Brand + New chat */}
       <Box sx={{ p: 1.5, display: "flex", flexDirection: "column", gap: 1 }}>
-        <Box sx={{ display: "flex", alignItems: "center", gap: 1, px: 0.5 }}>
-          <OdinMark size={28} />
-          <Typography variant="subtitle1" sx={{ fontWeight: 600 }}>
-            Odin
-          </Typography>
+        <Box
+          component="span"
+          sx={(t) => ({
+            px: 0.5,
+            fontSize: "1.7rem",
+            fontWeight: 700,
+            lineHeight: 1.2,
+            letterSpacing: "-0.02em",
+            backgroundImage: `linear-gradient(120deg, ${t.vars!.palette.primary.light}, ${t.vars!.palette.primary.main})`,
+            WebkitBackgroundClip: "text",
+            backgroundClip: "text",
+            WebkitTextFillColor: "transparent",
+          })}
+        >
+          Odin
         </Box>
         <Button fullWidth disabled={busy} onClick={onNew}>
           + Nová konverzace