feat(global) several major updates:

- delete page `tag`, `archive`
- add page `friends`
- implement page `about` *partially*

frontend/app/fetch.ts

@@ -0,0 +1,17 @@
+export async function fetchText(url: string, ttl: number = 600) {
+    const res = await fetch(url, {
+        next: {
+            revalidate: ttl
+        }
+    });
+    return await res.text();
+}
+
+export async function fetchJson(url: string, ttl: number = 600) {
+    const res = await fetch(url, {
+        next: {
+            revalidate: ttl
+        }
+    });
+    return await res.json();
+}