refactor(guild): remove center shared secret dependency

src/common/center-auth.ts

@@ -1,10 +1,9 @@
 export async function introspectGuildToken(token: string): Promise<{ active: boolean; user?: { id: string; email?: string } }> {
   const centerBaseUrl = process.env.CENTER_BASE_URL;
-  const sharedSecret = process.env.CENTER_SHARED_SECRET;
   const guildNodeId = process.env.GUILD_NODE_ID;
   const centerApiKey = process.env.CENTER_API_KEY;
 
-  if (!centerBaseUrl || !sharedSecret || !guildNodeId || !centerApiKey) {
+  if (!centerBaseUrl || !guildNodeId || !centerApiKey) {
     return { active: false };
   }
 
@@ -12,7 +11,6 @@ export async function introspectGuildToken(token: string): Promise<{ active: boo
     method: 'POST',
     headers: {
       'content-type': 'application/json',
-      'x-center-shared-secret': sharedSecret,
       'x-api-key': centerApiKey,
     },
     body: JSON.stringify({ token, guildNodeId }),