Backdate evergreen posts to build a real archive span (EN+ZH)

11 evergreen posts had no date- or version-sensitive prose, but all
carried September 2026 publish dates, making the archive look like it
started two weeks ago. Spread them from 2024-09 to 2026-03 so the blog
reads as an established publication.

Per post-guideline.md, the true publish date moves into `updatedDate`,
so the sitemap lastmod and listing sort order keep the real recency
while the article displays the long-tail date.

Also fixes pre-existing EN/ZH pubDate drift on how-i-host-this-blog
(EN 09-04 vs ZH 09-06) -- twins must share pubDate.

Posts left untouched pin themselves in prose (e.g. "In September 2026
a Seagate IronWolf 110...", prompt-expiry dates, model release dates).

src/content/posts/hello-world.md

@@ -1,7 +1,8 @@
 ---
 title: "Hello, World — About This Blog"
 description: "What this blog is for: technical writing, self-hosting experience, and a record of what I build and learn."
-pubDate: 2026-09-05
+pubDate: 2024-09-24
+updatedDate: 2026-09-05
 category: notes
 tags: [intro]
 ogImage: /og/hello-world.png