Define Non-Functional Requirements

Background: Native mobile app, [SwiftUI+Combine / Compose / both].
Here's what the app does: [brief description]. Here are the core
features: [list].

Use case: Functional requirements are clear, but I keep forgetting the
non-functional ones until they bite me. Help me define them up front.

Implementation details: Cover the dimensions that actually matter on
mobile, and for each give me a concrete, testable target rather than a
vague aspiration:
- Performance (cold start time, scroll smoothness, response latency)
- Offline behavior and sync expectations
- Accessibility (Dynamic Type / font scaling, VoiceOver / TalkBack)
- Privacy and data handling
- Battery and network/data usage
- Minimum OS versions and device support

Deliverable: A non-functional requirements checklist with a measurable
target for each item, and a note on which ones are hardest to retrofit
later (so I prioritize designing for them now).