fix(ui): add inner padding to strip components

Add px-3 to person bar, filter controls, and hint bar so inputs
don't sit flush against the container edge.

Refs: #179

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

frontend/src/routes/briefwechsel/CorrespondenzPersonBar.svelte

@@ -55,7 +55,7 @@ function handleSuggestionSelect(id: string) {
 
 <div
 	data-testid="conv-person-bar"
-	class="flex items-end gap-[9px] border-b border-line bg-surface py-[9px] [&_input]:h-12"
+	class="flex items-end gap-[9px] border-b border-line bg-surface px-3 py-[9px] [&_input]:h-12"
 >
 	<!-- Person A -->
 	<div class="min-w-0 flex-1">