content(website): add blog post for v1.12.1 (latest release) #405
Description
Problem
The latest release v1.12.1 has no blog post on the website. The homepage shows v1.12.1 but the blog/changelog section does not cover it.
Fix
Create website/src/content/blog/v1-12-1.md with release notes for v1.12.1, following the existing blog post format (see v1-12-0.md as a template).
CHANGELOG entry for v1.12.1 (2026-03-15): Website Performance & Mobile Optimization.