feat: implement complex selection flow

apps/backend/src/modules/complex/handlers/get-current-complex.handler.ts

@@ -0,0 +1,22 @@
+import { getCurrentComplex } from '@/modules/complex/services/complex.service';
+import type { AppContext } from '@/types/hono';
+import { getCookie } from 'hono/cookie';
+
+const SELECTED_COMPLEX_COOKIE = 'selected-complex-id';
+
+export async function getCurrentComplexHandler(c: AppContext) {
+  const user = c.get('user');
+  const complexId = getCookie(c, SELECTED_COMPLEX_COOKIE);
+
+  if (!complexId) {
+    return c.json(null);
+  }
+
+  const complex = await getCurrentComplex(user.id, complexId);
+
+  if (!complex) {
+    return c.json(null);
+  }
+
+  return c.json(complex);
+}