chore: clean up content phase organization

apps/docs/blume.config.ts

@@ -7,7 +7,13 @@ export default defineConfig({
     site: "https://prdlk.github.io",
     base: "/leetcode",
   },
+  lastModified: "git",
   content: {
     root: "content",
   },
+  navigation: {
+    sidebar: {
+      display: "flat", // "flat" | "group" | "page"
+    },
+  },
 });