Introduce ConnectionState enum (idle → authenticating → authenticated
→ destinationSelected → failed) replacing the old Bool isConnected flag.
The entire UI renders reactively from this single state value.
Authentication: vm.authenticate() drives the state, haptic feedback
fires on success, any field edit resets back to idle so the user always
knows their current auth is stale after editing.
Connected banner: slides in below the credentials card after auth
showing "Connected to [host]" with a green dot and a Disconnect button
that resets state without clearing credentials.
Destination row: always visible at 40% opacity with a lock icon and
placeholder text "Connect to your NAS first" — activates to full opacity
with chevron and browsable state after auth. Green border + subtitle
"Backup destination ready" appears after selection. Taps blocked via
allowsHitTesting until authenticated.
CTA progression:
idle/failed → "Connect" (enabled when fields filled)
authenticating → spinner, disabled
authenticated → "Choose Destination" (opens folder browser)
destinationSelected → "Get Started" in green → navigates to dashboard
After folder browser dismissal, confirmDestination() writes the path
to ConnectionStore and fires a light haptic. Navigation to MainTabView
happens only when state == .destinationSelected.
Co-Authored-By: Kutesir <kutesir@provoc.ug>
Co-Authored-By: Sentry <sentry@provoc.ug>
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