Generate User Stories & Acceptance Criteria

Background: Building a native mobile app. Here is the feature or epic
I'm specifying: [feature name and short description].

Use case: Write user stories with acceptance criteria detailed enough
that I (or an AI coding assistant) could implement them without guessing.

Implementation details:
- Use the format: "As a [user], I want [goal], so that [benefit]"
- Each story gets Given/When/Then acceptance criteria
- Include the unhappy paths: empty states, errors, offline, no permission
- Note any platform difference (e.g., iOS share sheet vs Android intents)

Deliverable: A set of user stories grouped by user flow. For each story
include acceptance criteria and a short "definition of done" checklist
(UI, state handling, error handling, accessibility, tests).