feat(odin): OdinChat orchestrator; render on /odin; remove DashAssistant

Wire OdinTabs/OdinThread/InvoiceReviewCard/OdinComposer into a single
OdinChat orchestrator; mount it on /odin (maxWidth 1100); delete the
old DashAssistant and its aiHistoryOptions query helper.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/admin/pages/Odin.tsx

@@ -2,7 +2,7 @@ import Box from "@mui/material/Box";
 import Typography from "@mui/material/Typography";
 import { PageEnter } from "../ui";
 import { useAuth } from "../context/AuthContext";
-import DashAssistant from "../components/dashboard/DashAssistant";
+import OdinChat from "../components/odin/OdinChat";
 
 export default function Odin() {
   const { hasPermission } = useAuth();
@@ -19,8 +19,8 @@ export default function Odin() {
 
   return (
     <PageEnter>
-      <Box sx={{ maxWidth: 920, mx: "auto" }}>
-        <DashAssistant />
+      <Box sx={{ maxWidth: 1100, mx: "auto" }}>
+        <OdinChat />
       </Box>
     </PageEnter>
   );