feat(tickets): add TicketsPage with URL-param filter state, stub detail panel and modal

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

frontend/src/components/tickets/NewTicketModal.tsx

@@ -0,0 +1,12 @@
+// Placeholder — full implementation in Task 17
+interface Props {
+  defaultTab?: 'quick' | 'manual'
+  initialValues?: Record<string, unknown>
+  summaryHint?: string
+  onClose: () => void
+  onCreated: (ticketId?: number, summary?: string) => void
+}
+
+export function NewTicketModal(_props: Props) {
+  return null
+}