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/app/(admin)/page.tsx

@@ -0,0 +1,64 @@
+// apps/admin/src/app/(admin)/page.tsx
+// CRM 대시보드 — 요약 카드 4개
+
+import { Box, Grid } from '@mui/material'
+import { MetalCard, PhosphorText } from '@d3ro/ui/components/ds'
+import { d3roPalette } from '@d3ro/ui/theme'
+import { getSupabaseServerClient } from '@/lib/supabase-server'
+
+interface StatCard {
+  label: string
+  value: string | number
+  color?: string
+}
+
+async function loadStats(): Promise<StatCard[]> {
+  const supabase = await getSupabaseServerClient()
+
+  const [profilesRes, paidRes, usageRes, expiringRes] = await Promise.all([
+    supabase.from('profiles').select('id', { count: 'exact', head: true }),
+    supabase.from('subscriptions').select('id', { count: 'exact', head: true })
+      .neq('tier', 'free').eq('status', 'active'),
+    supabase.from('daily_usage').select('count')
+      .eq('date', new Date().toISOString().split('T')[0]),
+    supabase.from('subscriptions').select('id', { count: 'exact', head: true })
+      .eq('status', 'active').eq('payment_provider', 'payple')
+      .lte('current_period_end', new Date(Date.now() + 7 * 86400000).toISOString()),
+  ])
+
+  const todayUsage = (usageRes.data as Array<{ count: number }> | null)
+    ?.reduce((sum, r) => sum + (r.count ?? 0), 0) ?? 0
+
+  return [
+    { label: 'TOTAL USERS', value: profilesRes.count ?? 0 },
+    { label: 'PAID SUBSCRIBERS', value: paidRes.count ?? 0, color: d3roPalette.tag.green },
+    { label: 'TODAY API CALLS', value: todayUsage, color: d3roPalette.accent.amber },
+    { label: 'EXPIRING (7D)', value: expiringRes.count ?? 0, color: d3roPalette.tag.red },
+  ]
+}
+
+export default async function AdminOverviewPage(): Promise<React.ReactElement> {
+  const stats = await loadStats()
+
+  return (
+    <Box>
+      <PhosphorText variant="title" sx={{ mb: 3 }}>OVERVIEW</PhosphorText>
+      <Grid container spacing={2}>
+        {stats.map((stat) => (
+          <Grid size={{ xs: 12, sm: 6, md: 3 }} key={stat.label}>
+            <MetalCard>
+              <Box sx={{ textAlign: 'center', py: 2 }}>
+                <PhosphorText variant="label" sx={{ mb: 1, display: 'block', color: d3roPalette.text.label }}>
+                  {stat.label}
+                </PhosphorText>
+                <PhosphorText variant="hero" sx={{ color: stat.color ?? d3roPalette.text.primary }}>
+                  {stat.value}
+                </PhosphorText>
+              </Box>
+            </MetalCard>
+          </Grid>
+        ))}
+      </Grid>
+    </Box>
+  )
+}