feat: rebuild site on Hugo + bonsai theme

Replace the custom Node.js builder with Hugo and the bonsai theme
(added as a submodule at themes/bonsai). Site content moves from
config.yaml into [params] in hugo.toml. CI switched to Hugo Extended
0.154.0 build; daily cron dropped (no API decoration to refresh).
Avatar imported from miti99 project.

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "themes/bonsai"]
+	path = themes/bonsai
+	url = https://github.com/tiennm99/bonsai.git