fix(auth): make DM pages server-rendered so middleware can set Astro.locals.user

Pages /dm/ and /ru/dm/ were static (prerendered), so middleware
never ran and Astro.locals.user was always null. Adding
prerender = false allows middleware to authenticate the user
before page render.

src/pages/dm/index.astro

@@ -1,4 +1,6 @@
 ---
+export const prerender = false;
+
 import DmLayout from "@/layouts/DmLayout.astro";
 import DmCard from "@/components/dm/DmCard.astro";
 import DiceRoller from "@/components/dm/DiceRoller.astro";

src/pages/ru/dm/index.astro

@@ -1,4 +1,6 @@
 ---
+export const prerender = false;
+
 import DmLayout from "@/layouts/DmLayout.astro";
 import DmCard from "@/components/dm/DmCard.astro";
 import DiceRoller from "@/components/dm/DiceRoller.astro";