feat: desktop messaging + pairing + cross-client master-pub attribution (v2.2.0-alpha5)

Two coordinated changes:

1. Desktop client gets a functional Messages section and working pairing
flow, putting it at feature parity with mobile for the v2.2.0 line.

2. Server + both clients teach each other to use the sender's master
Ed25519 (not just their X25519) to address conversations, so a peer
writing from a different linked device still rolls into the same chat.
This is the "new API logic" the desktop scaffold was waiting on.

Server (node/api_relay.go, cmd/node/main.go):
  * /relay/inbox items now carry `sender_ed25519_pub` alongside the
    per-device `sender_pub`. Empty string for pre-v2.2.0 senders.
  * WS `inbox` push summary also includes `sender_ed25519_pub`, so the
    client can skip the refetch when the envelope plainly isn't for
    the chat they're watching.
  * Both existing tests pass.

Mobile client:
  * lib/types.ts Envelope grew `sender_ed25519_pub`; fetchInbox normalises
    it (default '') for older nodes.
  * hooks/useGlobalInbox matches contacts by (master Ed25519 OR legacy
    X25519) so an incoming message from a peer's desktop reuses the
    existing chat instead of creating a duplicate placeholder.
  * hooks/useMessages now takes an optional `contactMasterEd25519` and
    exposes a matchesChat() predicate; WS inbox handler uses it too to
    avoid spurious refetches.
  * chats/[id].tsx passes `contact.address` (master) along with x25519.

Desktop client — all new:
  * src/lib/crypto.ts — tweetnacl hex/base64 helpers, generateKeyFile,
    encryptMessage/decryptMessage, signBase64, shortAddr. Same signatures
    as the mobile lib; uses Chromium's window.crypto, no expo-crypto dep.
  * src/lib/tx.ts — buildTransferTx / buildLinkDeviceTx / buildUnlinkDeviceTx
    + submitTx + humanizeTxError, canonical-bytes identical to mobile.
  * src/lib/relay.ts — fetchInbox, sendEnvelope, resolveRecipientKeys
    (multi-device fan-out with legacy identity.x25519 fallback).
  * src/lib/store.ts — zustand state gets messages{}, unread{},
    activeChat.
  * src/lib/storage.ts — per-chat cache via localStorage (500-msg cap).
  * src/hooks/useInboxPoll — 4s polling loop, addresses conversations
    by master Ed25519, bumps unread unless chat is active.
  * src/sections/messages/* — ChatList (sorted tiles, unread badges),
    Conversation (auto-scroll messages + composer + fan-out send,
    Enter-to-send / Shift+Enter for newline), EmptyConversation.
  * src/auth/Pair.tsx — 6-digit code + device key screen, polls inbox
    for a handshake envelope, assembles the KeyFile on arrival.
  * Welcome.tsx: Pair button now actually routes to <Pair>; imports
    generateKeyFile from lib/crypto (was inlined).

docs/ROADMAP.md delta: alpha5 row flipped to done inline. Alpha6
(feed + wallet) and rc1 (contacts + devices UI + profile) still
pending.

node/api_relay.go

@@ -90,27 +90,29 @@ func relayInboxList(rc RelayConfig) http.HandlerFunc {
 		}
 
 		type item struct {
-			ID           string `json:"id"`
-			SenderPub    string `json:"sender_pub"`
-			RecipientPub string `json:"recipient_pub"`
-			FeeUT        uint64 `json:"fee_ut,omitempty"`
-			SentAt       int64  `json:"sent_at"`
-			SentAtHuman  string `json:"sent_at_human"`
-			Nonce        []byte `json:"nonce"`
-			Ciphertext   []byte `json:"ciphertext"`
+			ID                 string `json:"id"`
+			SenderPub          string `json:"sender_pub"`           // X25519 hex
+			SenderEd25519Pub   string `json:"sender_ed25519_pub"`   // master Ed25519 hex (optional; may be empty for legacy senders)
+			RecipientPub       string `json:"recipient_pub"`
+			FeeUT              uint64 `json:"fee_ut,omitempty"`
+			SentAt             int64  `json:"sent_at"`
+			SentAtHuman        string `json:"sent_at_human"`
+			Nonce              []byte `json:"nonce"`
+			Ciphertext         []byte `json:"ciphertext"`
 		}
 
 		out := make([]item, 0, len(envelopes))
 		for _, env := range envelopes {
 			out = append(out, item{
-				ID:           env.ID,
-				SenderPub:    env.SenderPub,
-				RecipientPub: env.RecipientPub,
-				FeeUT:        env.FeeUT,
-				SentAt:       env.SentAt,
-				SentAtHuman:  time.Unix(env.SentAt, 0).UTC().Format(time.RFC3339),
-				Nonce:        env.Nonce,
-				Ciphertext:   env.Ciphertext,
+				ID:               env.ID,
+				SenderPub:        env.SenderPub,
+				SenderEd25519Pub: env.SenderEd25519PubKey,
+				RecipientPub:     env.RecipientPub,
+				FeeUT:            env.FeeUT,
+				SentAt:           env.SentAt,
+				SentAtHuman:      time.Unix(env.SentAt, 0).UTC().Format(time.RFC3339),
+				Nonce:            env.Nonce,
+				Ciphertext:       env.Ciphertext,
 			})
 		}