refactor(admin): CRM을 apps/admin 독립 프로젝트로 분리

- apps/web에서 admin 라우트/가드/sidebar 링크 제거
- apps/admin: 독립 Next.js 앱 (포트 3001)
  - 자체 login/unauthorized/auth callback
  - admin-sidebar: Overview/Users/Subscriptions/Usage
  - requireAdmin() 가드: profile.role='admin' 체크
- monorepo workspace에 apps/admin 등록

apps/admin/src/components/admin-sidebar.tsx

@@ -0,0 +1,96 @@
+'use client'
+
+// apps/admin/src/components/admin-sidebar.tsx
+// Admin CRM 사이드바
+
+import { usePathname, useRouter } from 'next/navigation'
+import { Box, List, ListItem, ListItemButton, ListItemIcon, ListItemText, Button } from '@mui/material'
+import DashboardIcon from '@mui/icons-material/Dashboard'
+import PeopleIcon from '@mui/icons-material/People'
+import SubscriptionsIcon from '@mui/icons-material/Subscriptions'
+import BarChartIcon from '@mui/icons-material/BarChart'
+import LogoutIcon from '@mui/icons-material/Logout'
+import { PhosphorText } from '@d3ro/ui/components/ds'
+import { d3roPalette, d3roFontMono } from '@d3ro/ui/theme'
+import { getSupabaseBrowserClient } from '@/lib/supabase-browser'
+
+const NAV_ITEMS = [
+  { key: 'overview', path: '/', label: 'Overview', icon: <DashboardIcon /> },
+  { key: 'users', path: '/users', label: 'Users', icon: <PeopleIcon /> },
+  { key: 'subscriptions', path: '/subscriptions', label: 'Subscriptions', icon: <SubscriptionsIcon /> },
+  { key: 'usage', path: '/usage', label: 'Usage', icon: <BarChartIcon /> },
+]
+
+export function AdminSidebar(): React.ReactElement {
+  const pathname = usePathname()
+  const router = useRouter()
+
+  const handleLogout = async (): Promise<void> => {
+    const supabase = getSupabaseBrowserClient()
+    await supabase.auth.signOut()
+    router.replace('/login')
+  }
+
+  return (
+    <Box sx={{
+      width: 220,
+      minHeight: '100vh',
+      bgcolor: d3roPalette.bg.sidebar,
+      borderRight: `1px solid ${d3roPalette.border.default}`,
+      display: 'flex',
+      flexDirection: 'column',
+    }}>
+      <Box sx={{ p: 2.5, borderBottom: `1px solid ${d3roPalette.border.default}` }}>
+        <PhosphorText variant="heading">D3RO ADMIN</PhosphorText>
+        <PhosphorText variant="dim" sx={{ display: 'block', mt: 0.5, fontSize: 10 }}>CRM Console</PhosphorText>
+      </Box>
+
+      <List sx={{ flex: 1, py: 1 }}>
+        {NAV_ITEMS.map((item) => {
+          const active = item.path === '/'
+            ? pathname === '/'
+            : pathname.startsWith(item.path)
+          return (
+            <ListItem key={item.key} disablePadding>
+              <ListItemButton
+                selected={active}
+                onClick={() => router.push(item.path)}
+                sx={{
+                  fontFamily: d3roFontMono,
+                  '&.Mui-selected': {
+                    bgcolor: d3roPalette.bg.inset,
+                    borderLeft: `3px solid ${d3roPalette.accent.amber}`,
+                  },
+                }}
+              >
+                <ListItemIcon sx={{ minWidth: 36, color: active ? d3roPalette.accent.amber : d3roPalette.text.inactive }}>
+                  {item.icon}
+                </ListItemIcon>
+                <ListItemText
+                  primary={item.label}
+                  primaryTypographyProps={{
+                    fontFamily: d3roFontMono,
+                    fontSize: 13,
+                    color: active ? d3roPalette.text.primary : d3roPalette.text.secondary,
+                  }}
+                />
+              </ListItemButton>
+            </ListItem>
+          )
+        })}
+      </List>
+
+      <Box sx={{ p: 2, borderTop: `1px solid ${d3roPalette.border.default}` }}>
+        <Button
+          fullWidth
+          size="small"
+          startIcon={<LogoutIcon />}
+          onClick={() => void handleLogout()}
+          sx={{ fontFamily: d3roFontMono, fontSize: 12, color: d3roPalette.text.secondary }}
+        >
+          Logout
+        </Button>
+      </Box>
+    </Box>
+  )
+}