feat(site): redesigned /download, releases and links moved from GitHub to Forgejo

- /download: the jar as an in-game item (pixel heart in an inventory slot, vanilla-style tooltip with version, size and SHA-256, copy button), spec list, three install steps, release timeline
- releases read through a cached nginx proxy (/api/releases): Forgejo's API has no CORS headers
- README, footer and landing links point to git.wihuk.pro/boba/LoVisual (the GitHub repo they used does not exist)
- release workflow publishes through the Forgejo API and ships lovisual.jar.sha256
- fix i18n interpolation placeholders ({{x}}) in the download strings

backend/deploy/nginx-lovisual-releases-cache.conf

@@ -0,0 +1,2 @@
+# Cache zone for the /api/releases proxy (see nginx-visual.loki-code.dev.conf).
+proxy_cache_path /var/cache/nginx/lv_releases levels=1 keys_zone=lv_releases:1m max_size=10m inactive=1h use_temp_path=off;