feat(groups): group chats, and a mesh rather than a star; release v6.1.1

A group is an orchestration layer over the pairwise sessions the app already
holds. It owns no transport and no shared key: every frame leaves over a chat
that is already SAS-verified and already ratcheted, so a removed member simply
stops being sent anything. Membership is a roster the admin signs, ordered by
epoch, and the safety code is a commit-then-reveal round over every member's
fingerprint and nonce.

Delivery was the part that did not match its own description. The admin held a
link to everyone and nobody else held a link to anybody, so the relay path — the
documented fallback — was in fact the entire topology, and the admin going away
partitioned the group. Now, once the code is confirmed, each pair without a link
dials one over that relay path. The descriptors are compact enough to ride a
group frame and are signed with the sender's group identity key, so the relaying
member can drop a dial but cannot substitute one. The member with the smaller
fingerprint dials, which is the whole glare protocol.

Mesh links are released without a human comparing digits. Twenty-eight codes for
a group of eight is not a check anyone performs; the guarantee moves rather than
disappears, since the descriptor was signed by a key the signed roster names and
the group code covers. markGroupLinkVerified refuses any session whose in-band
exchange has not completed and whose peer has not proved possession of that key.

An existing 1:1 chat between two members is adopted instead of re-dialled, via a
probe bound to that session's own key fingerprint so it cannot be replayed onto
another chat to impersonate its author.

Security fix: g_hello was accepted on any session from anyone who knew the group
id, so any member could publish an identity the admin never invited and have the
admin sign and broadcast a roster containing it. It is now accepted only on a
session an invitation went out on, which also confines it to a direct link.

Mesh connections are kept out of the chat registry and muted from the document
events the header listens to, so a routing detail cannot tear down the display of
a conversation the user actually opened.

src/components/ui/Roadmap.jsx

@@ -33,14 +33,14 @@ function Roadmap() {
           features: ["ECDH + DTLS + SAS triple-layer security", "ECDH P-384 + AES-GCM 256-bit encryption", "DTLS fingerprint verification", "SAS (Short Authentication String) verification", "Perfect Forward Secrecy with key rotation", "Enhanced MITM attack prevention", "Complete ASN.1 DER validation", "OID and EC point verification", "SPKI structure validation", "P2P WebRTC architecture", "Metadata protection", "100% open source code"] },
         { v: "v5.0", title: "Desktop Edition", sub: "Native desktop apps for Windows, macOS, and Linux", status: "released", date: "Early 2026",
           features: ["Windows desktop app (Tauri v2)", "macOS desktop app (Tauri v2)", "Linux AppImage support (Tauri v2)", "Real-time notifications", "Automatic reconnection", "Cross-device synchronization", "Improved UX/UI", "Support for files up to 100MB"] },
-        { v: "v5.5", title: "Secure Voice & Calls", sub: "Encrypted voice messages, audio calls, and video calls", status: "current", date: "Now",
+        { v: "v5.5", title: "Secure Voice & Calls", sub: "Encrypted voice messages, audio calls, and video calls", status: "released", date: "Early 2026",
           features: ["End-to-end encrypted voice messages", "1:1 encrypted audio calls (WebRTC)", "1:1 encrypted video calls (WebRTC)", "Perfect Forward Secrecy for live media", "SRTP/DTLS-protected media streams", "In-call SAS verification", "Call notifications and auto-reconnection", "Low-latency P2P media"] },
-        { v: "v6.0", title: "Mobile Edition", sub: "Native mobile apps for iOS and Android", status: "dev", date: "Q4 2026",
+        { v: "v6.0", title: "Group Communications", sub: "Group chats with preserved privacy", status: "current", date: "Now",
+          features: ["P2P group chats up to 8 participants", "Mesh delivery with signed relay fallback", "One group safety code, compared by everyone", "Commit-then-reveal ceremony against code grinding", "Per-group identity keys, ephemeral by design", "Signed membership with epoch ordering", "Signed messages, so a split transcript is provable", "No server, no shared group key, no history"] },
+        { v: "v6.5", title: "Mobile Edition", sub: "Native mobile apps for iOS and Android", status: "dev", date: "Q2 2027",
           features: ["iOS native app (Swift/SwiftUI)", "Android native app (Kotlin/Jetpack Compose)", "PWA support for mobile browsers", "Real-time push notifications", "Battery optimization", "Mobile-optimized UX/UI", "Offline message queuing", "Biometric authentication"] },
-        { v: "v6.5", title: "Quantum-Resistant Edition", sub: "Protection against quantum computers", status: "planned", date: "Q2 2027",
+        { v: "v7.0", title: "Quantum-Resistant Edition", sub: "Protection against quantum computers", status: "planned", date: "Q4 2027",
           features: ["Post-quantum cryptography CRYSTALS-Kyber", "SPHINCS+ digital signatures", "Hybrid scheme: classic + PQ", "Quantum-safe key exchange", "Updated hashing algorithms", "Migration of existing sessions", "Compatibility with v5.x", "Quantum-resistant protocols"] },
-        { v: "v7.0", title: "Group Communications", sub: "Group chats with preserved privacy", status: "planned", date: "Q4 2027",
-          features: ["P2P group connections up to 8 participants", "Mesh networking for groups", "Signal Double Ratchet for groups", "Anonymous groups without metadata", "Ephemeral groups (disappear after session)", "Cryptographic group administration", "Group member auditing"] },
         { v: "v7.5", title: "Decentralized Network", sub: "Fully decentralized network", status: "research", date: "2028",
           features: ["Node mesh network", "DHT for peer discovery", "Built-in onion routing", "Tokenomics and node incentives", "Governance via DAO", "Interoperability with other networks", "Cross-platform compatibility", "Self-healing network"] },
         { v: "v8.0", title: "AI Privacy Assistant", sub: "AI for privacy and security", status: "research", date: "2028+",