fix(topbar): fix overflow pill popup clipped and hidden behind pdf viewer

Remove overflow-hidden from the main flex row — the inner min-w-0 flex-1
overflow-hidden title container already handles truncation. Add relative z-10
to the topbar wrapper so it stacks above the pdf viewer. Pill is now hidden
below md (matching the chip row) and shows +N at md, +N weitere at lg+.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/OverflowPillButton.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
 import { tick } from 'svelte';
+import { m } from '$lib/paraglide/messages.js';
 import { clickOutside } from '$lib/actions/clickOutside';
 
 type Person = { id: string; firstName: string; lastName: string };
@@ -44,12 +45,12 @@ function handleKeydown(e: KeyboardEvent) {
 		type="button"
 		aria-haspopup="true"
 		aria-expanded={open}
-		aria-label="{extraCount} weitere Empfänger anzeigen"
+		aria-label={m.topbar_overflow_show({ count: extraCount })}
 		onclick={toggle}
 		onkeydown={handleKeydown}
 		class="inline-flex shrink-0 items-center rounded-full border border-line bg-muted px-2 py-0.5 text-[14px] font-bold text-ink-2 hover:bg-surface focus-visible:ring-2 focus-visible:ring-primary"
 	>
-		+{extraCount} weitere
+		+{extraCount}<span class="hidden lg:inline">&nbsp;{m.topbar_overflow_suffix()}</span>
 	</button>
 
 	{#if open}
@@ -57,7 +58,9 @@ function handleKeydown(e: KeyboardEvent) {
 			role="list"
 			class="absolute top-full left-0 z-50 mt-1 min-w-[160px] rounded-md border border-line bg-surface p-3 shadow-lg"
 		>
-			<p class="mb-2 text-[14px] font-bold tracking-wide text-ink-2 uppercase">Weitere Empfänger</p>
+			<p class="mb-2 text-[14px] font-bold tracking-wide text-ink-2 uppercase">
+				{m.topbar_overflow_heading()}
+			</p>
 			{#each persons as person (person.id)}
 				<div role="listitem">
 					<a