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/OdinThread.tsx

@@ -7,6 +7,7 @@ interface OdinThreadProps {
   turns: ChatTurn[];
   busy: boolean;
   loading: boolean;
+  greeting?: string;
   threadRef: React.RefObject<HTMLDivElement | null>;
 }
 
@@ -37,6 +38,7 @@ export default function OdinThread({
   turns,
   busy,
   loading,
+  greeting,
   threadRef,
 }: OdinThreadProps) {
   return (
@@ -79,34 +81,50 @@ export default function OdinThread({
             flexDirection: "column",
             alignItems: "center",
             justifyContent: "center",
-            gap: 2.5,
+            gap: 1.25,
             textAlign: "center",
             px: 2,
           }}
         >
-          <Box sx={{ display: "flex", alignItems: "center", gap: 2 }}>
-            <OdinMark size={52} />
-            <Box
-              component="span"
-              sx={(t) => ({
-                fontSize: "clamp(2rem, 1.2rem + 2.4vw, 2.75rem)",
-                fontWeight: 700,
-                lineHeight: 1.1,
-                letterSpacing: "-0.02em",
-                backgroundImage: `linear-gradient(120deg, ${t.vars!.palette.primary.light}, ${t.vars!.palette.primary.main})`,
-                WebkitBackgroundClip: "text",
-                backgroundClip: "text",
-                WebkitTextFillColor: "transparent",
-              })}
+          {greeting && (
+            <Typography
+              component="div"
+              sx={{
+                color: "text.secondary",
+                fontWeight: 500,
+                fontSize: "clamp(1rem, 0.85rem + 0.6vw, 1.25rem)",
+              }}
             >
-              Odin
-            </Box>
+              {greeting}
+            </Typography>
+          )}
+          <Box
+            component="span"
+            sx={(t) => ({
+              fontSize: "clamp(2.25rem, 1.4rem + 2.6vw, 3rem)",
+              fontWeight: 800,
+              lineHeight: 1.05,
+              letterSpacing: "-0.03em",
+              backgroundImage: `linear-gradient(120deg, ${t.vars!.palette.primary.light}, ${t.vars!.palette.primary.main})`,
+              WebkitBackgroundClip: "text",
+              backgroundClip: "text",
+              WebkitTextFillColor: "transparent",
+            })}
+          >
+            Odin
           </Box>
           <Typography
-            variant="body2"
-            sx={{ color: "text.secondary", maxWidth: 440 }}
+            component="div"
+            sx={{
+              color: "text.secondary",
+              maxWidth: 460,
+              mt: 0.5,
+              fontSize: "0.95rem",
+              lineHeight: 1.5,
+            }}
           >
-            Zeptejte se, nebo přiložte fakturu (PDF) k automatickému importu.
+            Váš firemní AI asistent. Zeptejte se, nebo přiložte fakturu (PDF) k
+            importu.
           </Typography>
         </Box>
       )}