feat: F5.2 sign-in with the dashboard's ticket and the service way

Server F checks the dashboard's entry ticket as itsdangerous does
(tools/ticket-oracle: tickets made by itsdangerous 2.2.0 itself), redeems
it at /__auth for a session cookie (only the key's SHA-256 is kept) and
decides at /sync by the session's grant: none, read or write; a frozen
project is read by everyone; every refusal names its reason (one list in
packages/protocol/src/sync.ts). A WebSocket from a page of another origin
is refused. /svc/* with the service key makes, deletes, freezes and
thaws projects, ends a person's grant or all their sessions (connections
let go) and lists the sessions. Snapshots, restoring and copying move to
F6 (they need the canonical doc.json and an epoch).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/server/test/tickets.ts

@@ -0,0 +1,15 @@
+// Tickets as the dashboard signs them, made in Node for the server's tests
+// (the Python oracle shows the same JSON at the same moment: ticket.test.ts).
+
+import { deflateSync } from 'node:zlib';
+import { signature, TICKET_SALT } from '../src/ticket.js';
+
+export function signTicket(payload: unknown, secret: string, at = Math.floor(Date.now() / 1000), salt = TICKET_SALT): string {
+  const json = Buffer.from(JSON.stringify(payload));
+  const packed = deflateSync(json);
+  const body = packed.length < json.length - 1 ? `.${packed.toString('base64url')}` : json.toString('base64url');
+  let stamp = Buffer.alloc(0);
+  for (let rest = at; rest > 0; rest = Math.floor(rest / 256)) stamp = Buffer.concat([Buffer.from([rest % 256]), stamp]);
+  const value = `${body}.${stamp.toString('base64url')}`;
+  return `${value}.${signature(value, secret, salt)}`;
+}