feat(odin): animated Odin brand mark (AI core orbiting business data)

A self-contained animated SVG mark in BOHA red: a 4-point AI spark (Odin) that
slow-rotates and breathes, a data node orbiting a faint ring (the assistant at
the centre of the business system). An "idle" and a "thinking" state (faster
orbit + red glow); honours prefers-reduced-motion. Used as the sidebar brand,
the empty-state hero, and the busy/thinking indicator.

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

src/admin/components/odin/OdinSidebar.tsx

@@ -5,6 +5,7 @@ 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 }[];
@@ -78,20 +79,7 @@ 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 }}>
-          <Box
-            sx={{
-              px: 0.75,
-              py: 0.25,
-              borderRadius: 1,
-              fontSize: 11,
-              fontWeight: 700,
-              letterSpacing: 0.5,
-              color: "common.white",
-              bgcolor: "primary.main",
-            }}
-          >
-            AI
-          </Box>
+          <OdinMark size={28} />
           <Typography variant="subtitle1" sx={{ fontWeight: 600 }}>
             Odin
           </Typography>