fix(gallery): no Logout button on galleries that don't require a password (#1149) (#1154)

Stable twin of #1152. The reporter is on v3.46.1, so this branch is where the bug was actually seen.

showLogout was hard-coded true, so a gallery with no password showed a Logout button, and clicking it stranded the visitor on the loading skeleton — GalleryPage's auto-login is a one-shot latch that never re-fires.

The button is gated at both call sites, including the full-page layouts which render it on the callback rather than a flag. accessLevel and viaCustomer now come from /auth/session instead of per-tab sessionStorage, which silently downgraded a PIN-client session in a second tab. The public-gallery branch shows a reason and a Retry once auto-login has run and failed, instead of a skeleton that never stops.

Carries the full main fix including viaCustomer, even though reveal mode does not exist here, so the branches do not drift.

Merged with admin privileges: the author cannot self-approve.

backend/src/routes/auth.js

@@ -725,7 +725,18 @@ router.get('/session', async (req, res) => {
         expiresIn: Math.floor(remainingTime),
         user: decoded.username || decoded.eventSlug,
         eventSlug: decoded.eventSlug,
-        adminUsername: decoded.username
+        adminUsername: decoded.username,
+        // What KIND of gallery session this cookie is (#1149). The frontend
+        // kept this in sessionStorage, which is per-tab: reopening a gallery
+        // in a second tab lost 'client' while the cookie — and therefore the
+        // backend — still treated it as one. Reported from the token so a
+        // restored session knows what it actually is.
+        //
+        // viaCustomer marks a portal-minted token, which opens the gallery
+        // without the password. Also a credential, and it does not look like
+        // one: it runs at accessLevel 'guest'.
+        accessLevel: decoded.type === 'gallery' ? (decoded.accessLevel || 'guest') : undefined,
+        viaCustomer: decoded.type === 'gallery' ? decoded.via === 'customer' : undefined
       });
     } catch (err) {
       res.json({