better server side signin redirects

this makes it so if a user requests a page (not API route) and isn't
signed in, it automatically redirects them to the sign in page (doesn't
show a flash of the error page)

server/plugins/redirect.ts

@@ -0,0 +1,24 @@
+import { H3Error } from "h3";
+
+export default defineNitroPlugin((nitro) => {
+  nitro.hooks.hook("error", async (error, { event }) => {
+    if (!event) return;
+
+    // Don't handle for API routes
+    if (event.path.startsWith("/api")) return;
+
+    // Make sure it's a web error
+    if (!(error instanceof H3Error)) return;
+
+    switch (error.statusCode) {
+      case 401:
+      case 403:
+        const userId = await event.context.session.getUserId(event);
+        if (userId) break;
+        return sendRedirect(
+          event,
+          `/signin?redirect=${encodeURIComponent(event.path)}`,
+        );
+    }
+  });
+});