feat: UI polish — AI enhancements branding, footer year, admin background fix

- Header: add "+ AI enhancements" italic subtitle below logo
- Footer: update copyright year to 2021–current, add "AI enhancements by Cloud Host" link
- Admin page: wrap all states in pageBg Box so dark-mode background shows correctly

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

components/Header.tsx

@@ -1,7 +1,7 @@
 import { FC } from "react";
 import Head from "next/head";
 import NextLink from "next/link";
-import { Flex, HStack, IconButton, Link, useColorModeValue } from "@chakra-ui/react";
+import { Flex, HStack, IconButton, Link, Text, VStack, useColorModeValue } from "@chakra-ui/react";
 import { FaGithub } from "react-icons/fa";
 import { FiSettings } from "react-icons/fi";
 import Image from "next/image";
@@ -28,13 +28,18 @@ const Header: FC<Props> = (props) => (
             {...props}
         >
             <NextLink href="/" passHref={true}>
-                <Link display="flex">
-                    <Image
-                        src={useColorModeValue("/banner_light.svg", "/banner_dark.svg")}
-                        alt="Logo"
-                        width={110}
-                        height={64}
-                    />
+                <Link display="flex" alignItems="center">
+                    <VStack spacing={0} align="flex-start">
+                        <Image
+                            src={useColorModeValue("/banner_light.svg", "/banner_dark.svg")}
+                            alt="Logo"
+                            width={110}
+                            height={64}
+                        />
+                        <Text fontSize="xs" fontStyle="italic" opacity={0.7} ml={1}>
+                            + AI enhancements
+                        </Text>
+                    </VStack>
                 </Link>
             </NextLink>
             <HStack spacing={3}>