chore: initial commit for v0.0.1

DChain single-node blockchain + React Native messenger client.

Core:
- PBFT consensus with multi-sig validator admission + equivocation slashing
- BadgerDB + schema migration scaffold (CurrentSchemaVersion=0)
- libp2p gossipsub (tx/v1, blocks/v1, relay/v1, version/v1)
- Native Go contracts (username_registry) alongside WASM (wazero)
- WebSocket gateway with topic-based fanout + Ed25519-nonce auth
- Relay mailbox with NaCl envelope encryption (X25519 + Ed25519)
- Prometheus /metrics, per-IP rate limit, body-size cap

Deployment:
- Single-node compose (deploy/single/) with Caddy TLS + optional Prometheus
- 3-node dev compose (docker-compose.yml) with mocked internet topology
- 3-validator prod compose (deploy/prod/) for federation
- Auto-update from Gitea via /api/update-check + systemd timer
- Build-time version injection (ldflags → node --version)
- UI / Swagger toggle flags (DCHAIN_DISABLE_UI, DCHAIN_DISABLE_SWAGGER)

Client (client-app/):
- Expo / React Native / NativeWind
- E2E NaCl encryption, typing indicator, contact requests
- Auto-discovery of canonical contracts, chain_id aware, WS reconnect on node switch

Documentation:
- README.md, CHANGELOG.md, CONTEXT.md
- deploy/single/README.md with 6 operator scenarios
- deploy/UPDATE_STRATEGY.md with 4-layer forward-compat design
- docs/contracts/*.md per contract

client-app/hooks/useContacts.ts

@@ -0,0 +1,80 @@
+/**
+ * Contacts + inbound request tracking.
+ *
+ * - Loads cached contacts from local storage on boot.
+ * - Subscribes to the address WS topic so a new CONTACT_REQUEST pulls the
+ *   relay contact list immediately (sub-second UX).
+ * - Keeps a 30 s polling fallback for nodes without WS or while disconnected.
+ */
+
+import { useEffect, useCallback } from 'react';
+import { fetchContactRequests } from '@/lib/api';
+import { getWSClient } from '@/lib/ws';
+import { loadContacts } from '@/lib/storage';
+import { useStore } from '@/lib/store';
+
+const FALLBACK_POLL_INTERVAL = 30_000;
+
+export function useContacts() {
+  const keyFile     = useStore(s => s.keyFile);
+  const setContacts = useStore(s => s.setContacts);
+  const setRequests = useStore(s => s.setRequests);
+  const contacts    = useStore(s => s.contacts);
+
+  // Load cached contacts from local storage once
+  useEffect(() => {
+    loadContacts().then(setContacts);
+  }, [setContacts]);
+
+  const pollRequests = useCallback(async () => {
+    if (!keyFile) return;
+    try {
+      const raw = await fetchContactRequests(keyFile.pub_key);
+
+      // Filter out already-accepted contacts
+      const contactAddresses = new Set(contacts.map(c => c.address));
+
+      const requests = raw
+        .filter(r => r.status === 'pending' && !contactAddresses.has(r.requester_pub))
+        .map(r => ({
+          from:      r.requester_pub,
+          // x25519Pub will be fetched from identity when user taps Accept
+          x25519Pub: '',
+          intro:     r.intro ?? '',
+          timestamp: r.created_at,
+          txHash:    r.tx_id,
+        }));
+
+      setRequests(requests);
+    } catch {
+      // Ignore transient network errors
+    }
+  }, [keyFile, contacts, setRequests]);
+
+  useEffect(() => {
+    if (!keyFile) return;
+    const ws = getWSClient();
+
+    // Initial load + low-frequency fallback poll (covers missed WS events,
+    // works even when the node has no WS endpoint).
+    pollRequests();
+    const interval = setInterval(pollRequests, FALLBACK_POLL_INTERVAL);
+
+    // Immediate refresh when a CONTACT_REQUEST / ACCEPT_CONTACT tx addressed
+    // to us lands on-chain. WS fan-out already filters to our address topic.
+    const off = ws.subscribe('addr:' + keyFile.pub_key, (frame) => {
+      if (frame.event === 'tx') {
+        const d = frame.data as { tx_type?: string } | undefined;
+        if (d?.tx_type === 'CONTACT_REQUEST' || d?.tx_type === 'ACCEPT_CONTACT') {
+          pollRequests();
+        }
+      }
+    });
+    ws.connect();
+
+    return () => {
+      clearInterval(interval);
+      off();
+    };
+  }, [keyFile, pollRequests]);
+}