Offline Custom List App Development

I need a cross-platform mobile application built for both Android and iOS that lets users create totally customizable, fully offline lists—think flexible to-do lists first, but easily adaptable to inventories, shopping, or anything else. Users must be able to add fields of these types: text, number, image, date, dropdown, checkbox, and barcodes captured with the device camera.

Core functions
• Instant search, multi-level sorting, and field-based filtering
• Automatic totals on any numeric column
• Local notifications and reminders (no server dependency)
• One-tap export to PDF, Excel, and CSV
• Modern, minimalist UI that flips seamlessly between Light and Dark modes
• Complete bilingual support: English LTR and Arabic RTL, including proper layout mirroring

Everything—data, logic, reminders—has to run without an internet connection. At hand-off I receive full ownership of the source code along with ready-to-publish builds for both stores.

Please outline your technical approach (preferred stack, offline data strategy, barcode integration, localization plan), a rapid timeline that meets my ASAP target, and a clear cost breakdown with any milestone suggestions.

I will share the detailed feature matrix once we confirm the fundamentals.