fix: allow guests to view public memo comments

Add ListMemoComments to public endpoints whitelist so unauthenticated
users can see public comments. The service layer already filters
comments by visibility (only PUBLIC for guests).

Fixes #5471

server/router/api/v1/acl_config.go

@@ -29,8 +29,9 @@ var PublicMethods = map[string]struct{}{
 	"/memos.api.v1.IdentityProviderService/ListIdentityProviders": {},
 
 	// Memo Service - public memos (visibility filtering done in service layer)
-	"/memos.api.v1.MemoService/GetMemo":   {},
-	"/memos.api.v1.MemoService/ListMemos": {},
+	"/memos.api.v1.MemoService/GetMemo":          {},
+	"/memos.api.v1.MemoService/ListMemos":        {},
+	"/memos.api.v1.MemoService/ListMemoComments": {},
 }
 
 // IsPublicMethod checks if a procedure path is public (no authentication required).