i18n(broadcast): translate DetailView via $_() — header, actions, stats grid, polling, preview

- Status pill routed through $_('broadcast.statuses.' + status); STATUS_LABELS import dropped (constants kept for non-Svelte callers)
- Sent-at / scheduled-for date pills with locale-aware date formatter
- Action buttons (Duplizieren / Abbrechen / Zur Übersicht)
- 5 stats labels (sent/opened/clicked/bounced/unsubscribed) with interpolated sublines (von {n}, {n} Öffnungen, etc.)
- Polling hints (Live-Update… / Letzte Aktualisierung: {time}) + error fallback + inline error message
- "Wie die Kampagne aussah" preview heading
- "Geplante Kampagne abbrechen?" confirm

Baselines: hardcoded 1112 → 1103 (9 cleared); missing-keys baseline +1 (broadcast.statuses.* dynamic key).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/i18n-missing-baseline.json

@@ -5,6 +5,7 @@
 	"apps/mana/apps/web/src/lib/components/PwaUpdatePrompt.svelte": 3,
 	"apps/mana/apps/web/src/lib/modules/ai-agents/ListView.svelte": 2,
 	"apps/mana/apps/web/src/lib/modules/ai-missions/ListView.svelte": 2,
+	"apps/mana/apps/web/src/lib/modules/broadcast/views/DetailView.svelte": 1,
 	"apps/mana/apps/web/src/lib/modules/credits/ListView.svelte": 1,
 	"apps/mana/apps/web/src/lib/modules/dreams/ListView.svelte": 1,
 	"apps/mana/apps/web/src/lib/modules/firsts/ListView.svelte": 2,