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>

frontend/src/routes/admin/+page.svelte

@@ -127,7 +127,6 @@
 
 	// Ban modal state
 	let banTarget = $state<UserSummary | null>(null);
-	let banHideUploads = $state(false);
 	let banSubmitting = $state(false);
 
 	// PIN reset state — `pinModal` holds the freshly-issued plaintext PIN. We forget it
@@ -254,14 +253,13 @@
 
 	function openBanModal(user: UserSummary) {
 		banTarget = user;
-		banHideUploads = false;
 	}
 
 	async function confirmBan() {
 		if (!banTarget) return;
 		banSubmitting = true;
 		try {
-			await api.post(`/host/users/${banTarget.id}/ban`, { hide_uploads: banHideUploads });
+			await api.post(`/host/users/${banTarget.id}/ban`, {});
 			toast(`${banTarget.display_name} wurde gesperrt.`, 'success');
 			banTarget = null;
 			users = await api.get<UserSummary[]>('/host/users');
@@ -416,17 +414,14 @@
 	{/if}
 </Modal>
 
-<!-- Ban modal — checkbox-bearing, so uses the Modal shell instead of ConfirmSheet. -->
+<!-- Ban modal — ban always hides now, so this is a plain confirm (no checkbox). -->
 <Modal open={banTarget !== null} titleId="admin-ban-modal-title" onClose={() => (banTarget = null)}>
 	{#if banTarget}
 		<h2 id="admin-ban-modal-title" class="mb-1 text-lg font-bold text-gray-900 dark:text-gray-100">Benutzer sperren</h2>
 		<p class="mb-4 text-sm text-gray-600 dark:text-gray-400">
-			Was soll mit den Uploads von <strong>{banTarget.display_name}</strong> passieren?
+			<strong>{banTarget.display_name}</strong> wird gesperrt: alle Uploads verschwinden aus
+			Galerie, Diashow und Export, und die Sitzung wird beendet. Rückgängig machbar über „Entsperren“.
 		</p>
-		<label class="mb-4 flex cursor-pointer items-center gap-3 rounded-lg border border-gray-200 p-3 dark:border-gray-700">
-			<input type="checkbox" bind:checked={banHideUploads} class="h-4 w-4 rounded border-gray-300 text-red-600 focus:ring-red-500 dark:border-gray-600" />
-			<span class="text-sm text-gray-700 dark:text-gray-300">Uploads aus der Galerie ausblenden</span>
-		</label>
 		<div class="flex gap-2">
 			<button onclick={() => (banTarget = null)} class="flex-1 rounded-lg border border-gray-300 py-2 text-sm text-gray-700 hover:bg-gray-50 active:bg-gray-100 dark:border-gray-700 dark:text-gray-300 dark:hover:bg-gray-800 dark:active:bg-gray-800">Abbrechen</button>
 			<button onclick={confirmBan} disabled={banSubmitting} class="flex-1 rounded-lg bg-red-600 py-2 text-sm font-medium text-white hover:bg-red-700 active:bg-red-700 disabled:opacity-50 dark:bg-red-500 dark:hover:bg-red-400 dark:active:bg-red-400">