fix(user-flow): close offline-queue, export, session, ban & realtime gaps

Comprehensive user-flow review across guest/host/admin roles, then fixes with
e2e regression guards. Highlights:

- Offline upload queue auto-resumes on reconnect: network errors keep items
  pending (not error), 4xx are terminal (no infinite retry), quota exhaustion
  returns a distinct 413; queue cap + dedup.
- Export lifecycle: release atomically locks uploads; reopen invalidates and
  re-release regenerates the keepsake; workers claim their job atomically so a
  reopen->re-release can't corrupt the ZIP; startup re-spawns interrupted
  exports.
- Sessions slide on activity (no 30-day cliff); JWT expiry deferred to the
  revocable session row; sign-out-everywhere + revoke-on-PIN-reset.
- Ban always hides content (v_feed / find_visible_media / export filter
  is_banned) but stays a read-only ban per USER_JOURNEYS §10 — sessions are
  not revoked, read access + keepsake download preserved.
- Realtime: server-clock SSE delta cursor; event-closed/opened drive the UI
  live; feed_delta rate-limited; like returns {liked, like_count} to fix
  multi-device drift; lightbox live comments; diashow delta backfill.
- Forgotten-PIN in-app request flow; simultaneous same-name join returns 409;
  quota increment is transactional; operator floor.

Adds e2e/specs/10-flow-review/ (offline resume, export integrity, deterministic
anti-race guard) and updates existing specs for the new contracts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/src/handlers/me.rs

@@ -55,6 +55,12 @@ pub struct MeContextDto {
     pub privacy_note: String,
     pub quota_enabled: bool,
     pub storage_quota_enabled: bool,
+    /// Uploads are locked (event closed) — the composer should show a locked state live
+    /// instead of letting a guest compose an upload only to eat a 403.
+    pub uploads_locked: bool,
+    /// The gallery has been released and the export snapshotted — uploads are permanently
+    /// closed for this run (release ⇒ lock, and reopening regenerates).
+    pub gallery_released: bool,
 }
 
 pub async fn get_context(
@@ -69,6 +75,11 @@ pub async fn get_context(
     let quota_enabled = config::get_bool(&state.config_cache, "quota_enabled", true).await;
     let storage_quota_enabled = config::get_bool(&state.config_cache, "storage_quota_enabled", true).await;
 
+    let event = crate::models::event::Event::find_by_slug(&state.pool, &state.config.event_slug)
+        .await?;
+    let uploads_locked = event.as_ref().map(|e| e.uploads_locked_at.is_some()).unwrap_or(false);
+    let gallery_released = event.as_ref().map(|e| e.export_released_at.is_some()).unwrap_or(false);
+
     Ok(Json(MeContextDto {
         user_id: user.id,
         display_name: user.display_name,
@@ -76,5 +87,7 @@ pub async fn get_context(
         privacy_note,
         quota_enabled,
         storage_quota_enabled,
+        uploads_locked,
+        gallery_released,
     }))
 }