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/OdinThread.tsx

@@ -1,7 +1,7 @@
 import Box from "@mui/material/Box";
 import Typography from "@mui/material/Typography";
-import CircularProgress from "@mui/material/CircularProgress";
 import type { ChatTurn } from "./types";
+import OdinMark from "./OdinMark";
 
 interface OdinThreadProps {
   turns: ChatTurn[];
@@ -84,7 +84,7 @@ export default function OdinThread({
             px: 2,
           }}
         >
-          <OdinAvatar size={44} />
+          <OdinMark size={56} />
           <Typography variant="body2" sx={{ color: "text.secondary" }}>
             Dobrý den, jsem Odin. Zeptejte se, nebo přiložte fakturu (PDF) k
             importu.
@@ -147,7 +147,7 @@ export default function OdinThread({
             color: "text.secondary",
           }}
         >
-          <CircularProgress size={14} />
+          <OdinMark size={22} state="thinking" />
           <Typography variant="caption" sx={{ color: "inherit" }}>
             Pracuji…
           </Typography>