feat: BIP-39 master seed for unified key derivation

Replace fragmented random key generation with a single 24-word BIP-39
mnemonic that deterministically derives all node keys: Ed25519 (DID),
secp256k1 (Nostr/Bitcoin), BIP-84 xprv (Bitcoin Core), and LND aezeed
entropy. New onboarding flow: seed generate → word verification → identity
naming. Restore path enabled via 24-word entry. Includes seed RPC handlers,
mock backend support, LND/Bitcoin Core wallet-from-seed integration, and
UI polish across settings and discover views.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

core/archipelago/src/main.rs

@@ -40,18 +40,15 @@ mod totp;
 mod wallet;
 mod names;
 mod network;
+pub mod seed;
 mod nostr_relays;
 mod update;
 mod vpn;
 mod webhooks;
 
-use auth::AuthManager;
 use config::Config;
 use server::Server;
 
-/// Default dev password when auto-creating a user (matches mock-backend).
-const DEV_DEFAULT_PASSWORD: &str = "password123";
-
 #[tokio::main]
 async fn main() -> Result<()> {
     let startup_start = std::time::Instant::now();