Implements mobile Nostr identity management per issue #29.
Android — NIP-55 Amber integration:
- Opens com.greenart7c3.nostrsigner via `nostrsigner:` URI scheme to
retrieve the user's public key without exposing it to the app.
- Listens for the `mobile://nostr-callback` deep link response and stores
the resulting npub in Expo SecureStore.
- Falls back to Play Store install prompt when Amber is not installed.
iOS / manual fallback:
- NostrConnectModal accepts an nsec1 paste-in, validates bech32, derives
the pubkey via nostr-tools getPublicKey, and stores the key only in
Expo SecureStore — never in AsyncStorage, Redux, or logs.
Both platforms:
- Truncated npub and signer type (Amber / nsec) shown in Settings.
- "Disconnect Nostr" wipes all keys from SecureStore and resets state.
- Identity persists across restarts via SecureStore.
Supporting changes:
- NostrContext: new React context for identity lifecycle.
- NostrConnectModal: platform-aware bottom-sheet modal for connect flow.
- TimmyContext: added apiBaseUrl/setApiBaseUrl/isConnected; URL persisted
in AsyncStorage and restored on mount; circular dep broken via refs.
- constants/colors: added field, textInverted, destructive, link colours.
- constants/storage-keys: added SERVER_URL_KEY.
- app.json: added Android intent filter for mobile://nostr-callback.
- package.json: added nostr-tools and expo-secure-store dependencies.
Fixes#29
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
