feat(onboarding): WebP-hero story flow, no cold-start permission ambush

[epicexcelsior]

What

The first 60 seconds, rebuilt — story-first, no permission ambush.

• Three story pages with a looping WebP scene hero (pigeon flyover / flock / recede, crossfaded via expo-image) → connect → a real backup step → BLE rationale step before any OS dialog.
• The cold-start permission ambush is gone: no location / nearby-devices dialog before the user has seen any content.
• Lands in Messages with a live first-run card (mesh count + invite a friend) instead of an empty-contacts dead end.
• Hero is animated WebP, not video — the expo-video decoder was freezing to a black screen; WebP scenes loop deterministically.

Scope

onboarding components (IntroHero/BackupStep/RadioStep/ScreenFade; removed AsciiBackground/GlowOrbs/LoadingOverlay/IntroVideo), app/onboarding.tsx, scene WebP assets, PeersDrawer first-run card, LxmfContext radio-consent wiring, NodesScreen.

Test

tsc clean · tier0 config/services clean · fake-money + lint clean. Conflict resolution (onboarding-lane vs the 6 already-merged lanes) was cross-checked against the tier0-green integration branch. Device pass is auth-gated, per plan. The now-unused expo-video dep is left for a lockfile-safe follow-up removal.

Note

Squashed from the onboarding lane's 24 commits (which added then removed expo-video mid-stream) into one clean diff.