feat: add copy/duplicate trip from dashboard (#270)

New POST /api/trips/:id/copy endpoint that deep copies all trip
planning data (days, places, assignments, reservations, budget,
packing, accommodations, day notes) with proper FK remapping
inside a transaction. Skips files, collab data, and members.

Copy button on all dashboard card types (spotlight, grid, list,
archived) gated by trip_create permission. Translations for all
12 languages.

Also adds reminder_days to Trip interface (removes as-any casts).

server/src/types.ts

@@ -31,6 +31,7 @@ export interface Trip {
   currency: string;
   cover_image?: string | null;
   is_archived: number;
+  reminder_days: number;
   created_at?: string;
   updated_at?: string;
 }