fix(audit): restore broken upload pipeline + role-based E2E audit fixes

A comprehensive role-based E2E audit (guest/host/admin, across browser
sessions) surfaced one critical and several smaller issues; this addresses
them and hardens the tests that missed them.

Critical
- The client upload pipeline was fully broken: the IndexedDB v1->v2 upgrade
  opened a *new* transaction inside the upgrade callback, which throws during
  a version-change transaction and aborted the whole upgrade, leaving the
  queue object store uncreated -- so no UI upload ever fired. Reuse the
  version-change transaction the callback provides, and bump the DB to v3 with
  a contains() guard so installs already corrupted by the shipped bug
  self-heal on next load. Re-enabled the previously-fixme'd UI upload E2E test.

High / Medium
- Event lock is uploads-only again: likes, comments and browsing stay open
  while the event is locked (USER_JOURNEYS 9.3 / FEATURES) -- it was wrongly
  freezing social interaction. Updated the event-lock spec accordingly.
- get_original now excludes soft-deleted and ban-hidden uploads, and direct
  /media/originals/** serving is blocked, so a hidden user's originals can no
  longer be pulled by UUID (all originals go through the checked alias).
- The upload handler reads the file field with an early-abort size cap chosen
  from the declared content-type, instead of buffering the entire body before
  the size check.

Low
- unban_user mirrors the ban role guard (a host can no longer unban a
  host/admin banned by an admin).
- reset_user_pin's UPDATE is event-scoped.
- Admin login returns and stores a real identity (user_id + display name)
  instead of a blank session.
- The host user list no longer renders target-actions (ban/promote/demote/PIN)
  on the caller's own row, where the backend always rejected them.
- /diashow gains a client-side auth guard like the other protected routes.
- The join page shows the event name via a new public GET /api/v1/event.

Verified: backend cargo build clean, frontend svelte-check 0 errors, full
Playwright E2E suite 144 passed / 1 skipped.

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

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

@@ -18,9 +18,14 @@
 		loading = true;
 		error = '';
 		try {
-			const res = await api.post<{ jwt: string }>('/admin/login', { password });
-			// Admin sessions have no PIN; pass null so setAuth doesn't overwrite a guest PIN
-			setAuth(res.jwt, null, '');
+			const res = await api.post<{ jwt: string; user_id: string; display_name: string }>(
+				'/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);
 			goto('/admin');
 		} catch (e) {
 			if (e instanceof ApiError) {

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

@@ -2,6 +2,7 @@
 	import { onMount, onDestroy } from 'svelte';
 	import { goto } from '$app/navigation';
 	import { api } from '$lib/api';
+	import { getToken } from '$lib/auth';
 	import { showBottomNav } from '$lib/ui-store';
 	import { dataMode, pickMediaUrl } from '$lib/data-mode-store';
 	import { onSseEvent } from '$lib/sse';
@@ -151,6 +152,13 @@
 	}
 
 	onMount(() => {
+		// Auth guard — mirror the other protected routes. Without this an
+		// unauthenticated visitor lands on a permanently-loading empty slideshow
+		// instead of being sent to /join.
+		if (!getToken()) {
+			goto('/join');
+			return;
+		}
 		showBottomNav.set(false);
 		void acquireWakeLock();
 		unsubs.push(onSseEvent('upload-processed', handleUploadProcessed));

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

@@ -1,6 +1,6 @@
 <script lang="ts">
 	import { goto } from '$app/navigation';
-	import { getToken, getRole } from '$lib/auth';
+	import { getToken, getRole, getUserId } from '$lib/auth';
 	import { api } from '$lib/api';
 	import type { MeContextDto } from '$lib/types';
 	import { onMount } from 'svelte';
@@ -57,6 +57,7 @@
 	let pinModal = $state<{ name: string; pin: string } | null>(null);
 
 	const myRole = getRole();
+	const myUserId = getUserId();
 
 	// Generic confirm-then-run for the irreversible / privilege-changing actions
 	// (promote, demote, unban, release gallery) that previously fired on one tap.
@@ -486,7 +487,11 @@
 													>
 														Entsperren
 													</button>
-												{:else}
+												{:else if user.id !== myUserId}
+													<!-- Never render target-actions (promote/demote/PIN/ban) on the
+													     caller's own row: the backend rejects every self-action
+													     (self-ban / self-demote / self-PIN) with a 400, so the button
+													     would only ever fail. -->
 													{#if user.role === 'guest' && (myRole === 'host' || myRole === 'admin')}
 														<button
 															onclick={() => (confirmAction = {

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

@@ -1,9 +1,21 @@
 <script lang="ts">
+	import { onMount } from 'svelte';
 	import { goto } from '$app/navigation';
 	import { api, ApiError } from '$lib/api';
 	import { setAuth } from '$lib/auth';
 	import { focusTrap } from '$lib/actions/focus-trap';
 
+	// Show which event the guest is joining (USER_JOURNEYS §1). Public, pre-auth.
+	let eventName = $state('');
+	onMount(async () => {
+		try {
+			const ev = await api.get<{ name: string; slug: string }>('/event');
+			eventName = ev.name;
+		} catch {
+			// Non-fatal — fall back to the generic heading if the lookup fails.
+		}
+	});
+
 	let displayName = $state('');
 	let error = $state('');
 	let loading = $state(false);
@@ -164,6 +176,9 @@
 		{:else}
 			<!-- Normal join form -->
 			<h1 class="mb-2 text-center text-2xl font-bold text-gray-900 dark:text-gray-100">Willkommen!</h1>
+			{#if eventName}
+				<p class="mb-1 text-center text-lg font-semibold text-blue-600 dark:text-blue-400" data-testid="join-event-name">{eventName}</p>
+			{/if}
 			<p class="mb-6 text-center text-gray-600 dark:text-gray-400">Gib deinen Namen ein, um dem Event beizutreten.</p>
 
 			<form onsubmit={(e) => { e.preventDefault(); handleJoin(); }}>