Settings screen (notifications, data export, about)

[ryanabooth]

The app has no Settings surface today. Add one.

Scope

Gear icon on every tab's nav bar (or a dedicated tab if we want to invest). Sections:

Notifications

• Master toggle (mirrors system permission)
• Per-type toggles:
  • Habit reminders
  • Plot wither / death alerts
  • Streak milestone celebrations
• Deep-link to system Settings if permission denied

Data

• Export all data as JSON — UIActivityViewController share sheet with a .json file: every model except FarmState derived state, suitable for backup. Includes a schema version so future imports can migrate.
• Import from JSON — read a file, merge or replace (warn user). Defer if scope balloons.
• Reset farm — destructive, requires double-confirmation. Wipes the model store and re-bootstraps.

About

• App version + build number (read from Info.plist)
• Link to docs/asset-spec.md (when hosted)
• Link to roadmap / GitHub issues
• Acknowledgements

Implementation notes

• New SettingsView under LifePlanner/UI/Settings/
• New SettingsInteractor for the destructive operations (export, import, reset) — or extend an existing one
• JSON export: JSONEncoder against a flat DTO struct; don't try to encode @Model types directly

Acceptance criteria

• Settings reachable from at least one tab
• Each notification toggle persists across launches
• Export produces a valid JSON file the user can read
• Reset farm restores the app to first-launch state (FarmState reseeded, all data gone)