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>

neode-ui/src/components/ToggleSwitch.vue

@@ -3,6 +3,8 @@
     type="button"
     role="switch"
     :aria-checked="modelValue"
+    tabindex="-1"
+    data-controller-ignore
     class="w-10 h-6 rounded-full shrink-0 transition-colors relative"
     :class="modelValue ? 'bg-orange-500' : 'bg-white/15'"
     @click="$emit('update:modelValue', !modelValue)"