refactor(admin): split architecture page.tsx into colocated components

Extract DetailPanel, ArchHeader, Toolbar, ArchCanvas and ServiceTable into
_components/, the ReactFlow node/edge builder into _hooks/useArchGraph, and
layout constants/helpers into _layout.ts. page.tsx drops from 950 to 91 LOC,
well below the 300 soft target.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

admin-compliance/app/sdk/architecture/_components/ArchHeader.tsx

@@ -0,0 +1,33 @@
+'use client'
+
+export default function ArchHeader({
+  stats,
+}: {
+  stats: {
+    services: number
+    dbTables: number
+    ragCollections: number
+    edges: number
+  }
+}) {
+  return (
+    <div className="bg-white rounded-xl border border-slate-200 p-5 shadow-sm">
+      <div className="flex items-center gap-4">
+        <div className="w-12 h-12 rounded-xl bg-slate-700 flex items-center justify-center text-white">
+          <svg className="w-7 h-7" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={1.5}
+              d="M5 12h14M5 12a2 2 0 01-2-2V6a2 2 0 012-2h14a2 2 0 012 2v4a2 2 0 01-2 2M5 12a2 2 0 00-2 2v4a2 2 0 002 2h14a2 2 0 002-2v-4a2 2 0 00-2-2m-2-4h.01M17 16h.01" />
+          </svg>
+        </div>
+        <div>
+          <h2 className="text-xl font-bold text-slate-900">
+            Architektur-Uebersicht
+          </h2>
+          <p className="text-sm text-slate-500">
+            {stats.services} Services | {stats.dbTables} DB-Tabellen | {stats.ragCollections} RAG-Collections | {stats.edges} Verbindungen
+          </p>
+        </div>
+      </div>
+    </div>
+  )
+}