feat: add global and per-post timezone support (#491)

* refactor: replace embedded svg with svg icon

* feat: add global and per-post timezone support

- add `SITE.timezone` in config to define a global default timezone.
- allow per-post timezone overrides via `timezone` in frontmatter.
- update date formatting logic to use the correct timezone when rendering timestamps.
- ensure that posts without a timezone fallback to `SITE.timezone`.
- improve consistency between local and deployed timezones.

* refactor: replace `LOCALE` constant with  `SITE.lang`

* docs: update guides

* fix: update code word-break inside markdown table

Closes #466

src/constants.ts

@@ -8,11 +8,6 @@ import IconTelegram from "@/assets/icons/IconTelegram.svg";
 import IconPinterest from "@/assets/icons/IconPinterest.svg";
 import { SITE } from "@/config";
 
-export const LOCALE = {
-  lang: "en", // html lang code. Set this empty and default will be "en"
-  langTag: ["en-EN"], // BCP 47 Language Tags. Set this empty [] to use the environment default
-} as const;
-
 export const SOCIALS = [
   {
     name: "Github",