Merge branch 'plan/e2ee' - End-to-end encryption for relay connections

Implements E2EE for relay connections only, keeping direct connections
and CLI plaintext. The relay acts as a dumb byte forwarder with no
access to decrypted messages.

Key changes:
- Daemon keypair persistence in $PASEO_HOME/daemon-keypair.json
- Encrypted relay transport using ECDH P-256 + AES-256-GCM
- Client-side E2EE using daemon's public key from pairing offer
- WebCrypto compatibility for React Native

packages/server/src/shared/connection-offer.ts

@@ -0,0 +1,16 @@
+import { z } from "zod";
+
+export const ConnectionOfferV1Schema = z.object({
+  v: z.literal(1),
+  sessionId: z.string().min(1),
+  endpoints: z.array(z.string().min(1)).min(1),
+  daemonPublicKeyB64: z.string().min(1),
+  relay: z
+    .object({
+      endpoint: z.string().min(1),
+    })
+    .nullable()
+    .optional(),
+});
+
+export type ConnectionOfferV1 = z.infer<typeof ConnectionOfferV1Schema>;

packages/server/src/shared/daemon-endpoints.ts

@@ -0,0 +1,117 @@
+export type HostPortParts = {
+  host: string;
+  port: number;
+  isIpv6: boolean;
+};
+
+export type RelayRole = "server" | "client";
+
+function parsePort(portStr: string, context: string): number {
+  const port = Number(portStr);
+  if (!Number.isInteger(port) || port < 1 || port > 65535) {
+    throw new Error(`${context}: port must be between 1 and 65535`);
+  }
+  return port;
+}
+
+export function parseHostPort(input: string): HostPortParts {
+  const trimmed = input.trim();
+  if (!trimmed) {
+    throw new Error("Host is required");
+  }
+
+  // IPv6: [::1]:6767
+  if (trimmed.startsWith("[")) {
+    const match = trimmed.match(/^\[([^\]]+)\]:(\d{1,5})$/);
+    if (!match) {
+      throw new Error("Invalid host:port (expected [::1]:6767)");
+    }
+    const host = match[1].trim();
+    if (!host) throw new Error("Host is required");
+    const port = parsePort(match[2], "Invalid host:port");
+    return { host, port, isIpv6: true };
+  }
+
+  const match = trimmed.match(/^(.+):(\d{1,5})$/);
+  if (!match) {
+    throw new Error("Invalid host:port (expected localhost:6767)");
+  }
+  const host = match[1].trim();
+  if (!host) throw new Error("Host is required");
+  const port = parsePort(match[2], "Invalid host:port");
+  return { host, port, isIpv6: false };
+}
+
+export function normalizeHostPort(input: string): string {
+  const { host, port, isIpv6 } = parseHostPort(input);
+  return isIpv6 ? `[${host}]:${port}` : `${host}:${port}`;
+}
+
+export function deriveLabelFromEndpoint(endpoint: string): string {
+  try {
+    const { host } = parseHostPort(endpoint);
+    return host || "Unnamed Host";
+  } catch {
+    return "Unnamed Host";
+  }
+}
+
+function shouldUseSecureWebSocket(port: number): boolean {
+  return port === 443;
+}
+
+export function buildDaemonWebSocketUrl(endpoint: string): string {
+  const { host, port, isIpv6 } = parseHostPort(endpoint);
+  const protocol = shouldUseSecureWebSocket(port) ? "wss" : "ws";
+  const hostPart = isIpv6 ? `[${host}]` : host;
+  return `${protocol}://${hostPart}:${port}/ws`;
+}
+
+export function buildRelayWebSocketUrl(params: {
+  endpoint: string;
+  sessionId: string;
+  role: RelayRole;
+}): string {
+  const { host, port, isIpv6 } = parseHostPort(params.endpoint);
+  const protocol = shouldUseSecureWebSocket(port) ? "wss" : "ws";
+  const hostPart = isIpv6 ? `[${host}]` : host;
+  const url = new URL(`${protocol}://${hostPart}:${port}/ws`);
+  url.searchParams.set("session", params.sessionId);
+  url.searchParams.set("role", params.role);
+  return url.toString();
+}
+
+export function extractHostPortFromWebSocketUrl(wsUrl: string): string {
+  const parsed = new URL(wsUrl);
+  if (parsed.protocol !== "ws:" && parsed.protocol !== "wss:") {
+    throw new Error("Invalid WebSocket URL protocol");
+  }
+  if (parsed.pathname.replace(/\/+$/, "") !== "/ws") {
+    throw new Error("Invalid WebSocket URL (expected /ws path)");
+  }
+
+  const host = parsed.hostname;
+  const port = parsed.port ? Number(parsed.port) : parsed.protocol === "wss:" ? 443 : 80;
+  if (!host) {
+    throw new Error("Invalid WebSocket URL (missing hostname)");
+  }
+  if (!Number.isInteger(port) || port < 1 || port > 65535) {
+    throw new Error("Invalid WebSocket URL (invalid port)");
+  }
+
+  const isIpv6 = host.includes(":") && !host.startsWith("[") && !host.endsWith("]");
+  return isIpv6 ? `[${host}]:${port}` : `${host}:${port}`;
+}
+
+export function isRelayClientWebSocketUrl(url: string): boolean {
+  try {
+    const parsed = new URL(url);
+    return (
+      parsed.searchParams.get("role") === "client" &&
+      parsed.searchParams.has("session")
+    );
+  } catch {
+    return false;
+  }
+}
+