release: v0.13.0 (#535)

Twenty-nine commits since v0.12.0. See CHANGELOG.md for the full list
and the upgrade notes.

Ten additions — the SEO package (site URL, robots.txt, sitemap.xml,
JSON-LD), slideshow mode, opt-in original downloads, copy-link,
previous/next album navigation, alt text from the Immich description,
per-album location precision, the update notice, a Help tab, and a
subpage cover grid separate from its photo grid. Two fixes: CJK album
slugs, and the lightbox control bar.

Photo of the Day (#476) was built on `dev` and reverted as not planned;
it never appears in a release.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

https://claude.ai/code/session_01DmsHVRL9yQvckUB1ZpVWre

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Co-authored-by: ralksta <ralksta@users.noreply.github.com>
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Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

.env.local.example

@@ -68,6 +68,20 @@ AUTH_SECRET=change-me-to-a-long-random-string
 # Leave unset or empty to disable the admin UI entirely.
 # ADMIN_PASSWORD=your-secure-admin-password
 
+# ── Site URL ─────────────────────────────────────────────────────
+# Used for sitemap.xml, the feed and structured data when `url:` is not
+# set in settings.yaml. The settings file takes precedence, so the admin
+# panel's field always does what it appears to do.
+# SITE_URL=https://folio.example
+
+# ── Update notice ────────────────────────────────────────────────
+# The admin dashboard compares the running version against the latest
+# GitHub release and shows the result in the status list. One request a
+# day, cached, and it fails quietly when there is no network.
+# Set to false to switch it off — the dashboard then only names the
+# version it is running.
+# UPDATE_CHECK=false
+
 # ── Site password (optional) ─────────────────────────────────────
 # Puts the WHOLE public site behind one password. Overrides
 # `sitePassword` in settings.yaml, so it can be rotated without