chore: bump theme submodule (fix excerpt frontmatter in listings)

Co-Authored-By: Claude Sonnet 4.6 <redacted>

diff --git a/themes/danix-xyz-hacker b/themes/danix-xyz-hacker
index 504b0cb102d87530cd1363cc00f5ca75e093e219..26840ef7057e42bd4d7aa02201a121f9ac47515d 160000 (submodule)
--- a/themes/danix-xyz-hacker
+++ b/themes/danix-xyz-hacker
@@ -1 +1 @@
-Subproject commit 504b0cb102d87530cd1363cc00f5ca75e093e219
+Subproject commit 26840ef7057e42bd4d7aa02201a121f9ac47515d