fix(user-flow): persona-audit fixes — ban replay, locked-upload data loss, host UX, admin session

Follows the perf + security + user-flow work with a role/persona audit (guest, host,
admin, projector) and fixes across three review rounds. Highlights:

HIGH
- Ban now replays on reconnect. A ban isn't a soft-delete, and the `user-hidden` SSE has
  no replay, so a client that missed it (esp. the unattended diashow) kept cycling a
  banned user's slides. New `uploads_hidden_at` (migration 013) + `hidden_user_ids` in
  /feed/delta; feed + diashow evict those users. Applied even on a truncated delta.

MEDIUM
- Locked-upload data loss: a photo staged offline during a lock/release was purged as a
  terminal 4xx and lost when the host reopened. New reversible `uploads_locked` error code;
  the queue keeps the blob and auto-resumes on the `event-opened` SSE.
- Reopen after release now warns (ConfirmSheet) that it revokes the published keepsake.
- Host "forgotten-PIN" badge updates live (`pin-reset-requested` was broadcast but never
  in KNOWN_EVENTS / subscribed); host page also refetches on `pin-reset` so a two-host
  race can't hand out a conflicting PIN.
- Ban modal copy fixed (read-only ban, not "session ended"); Degradieren/Sperren/Entsperren
  hidden on peer-host rows for non-admins (they always 403'd).
- Host dashboard shows live keepsake generation progress / ready state + link to /export.
- Admin JWT moved to sessionStorage (§11.1) to bound exposure on shared devices.

Export generation guard (H1 from the prior round, hardened): per-(event,type) `release_seq`
(migration 012) with seq-guarded claim/finalize/mark_failed/update_progress, per-generation
temp/final paths, download follows `file_path`, prune only strictly-older generations.

LOW: diashow coalesces upload-processed (avoids self-rate-limit); event-closed reconciles
galleryReleased; /recover gains a forgot-PIN request + drops a stale cached PIN on 401;
delta `>=` tie-break + 429 retry; misc copy/labels.

Adds e2e: ban-replay, upload-lock-code, and rewrites export-reopen-rerelease with a
data-completeness test. Reconciles USER_JOURNEYS §9/§11.

Verified: cargo build clean, 40 unit tests, svelte-check 0 errors, 33 frontend unit
tests, 155 e2e passing on chromium-desktop.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

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

@@ -1,7 +1,7 @@
 <script lang="ts">
 	import { goto } from '$app/navigation';
 	import { api, ApiError } from '$lib/api';
-	import { setAuth, getRole } from '$lib/auth';
+	import { setAdminAuth, getRole } from '$lib/auth';
 	import { browser } from '$app/environment';
 
 	// Already logged in as admin → go straight to dashboard
@@ -22,10 +22,10 @@
 				'/admin/login',
 				{ password }
 			);
-			// Admin sessions have no PIN; pass null so setAuth doesn't overwrite a guest PIN.
-			// Persist the real user id + name so the admin has an identity (own-post
-			// affordances on the feed, a name on the Account page rather than "Unbekannt").
-			setAuth(res.jwt, null, res.user_id, res.display_name);
+			// Admin session goes in sessionStorage (bounded to the tab; §11.1), with the real
+			// user id + name so the admin has an identity (own-post affordances on the feed, a
+			// name on the Account page rather than "Unbekannt"). No PIN for admins.
+			setAdminAuth(res.jwt, res.user_id, res.display_name);
 			goto('/admin');
 		} catch (e) {
 			if (e instanceof ApiError) {