Implement CHUNK #2: server layer, core schemas/adapters, contract tests, seed

Complete the server-backed storage layer for PubScript so the app can run
against a real Fastify + SQLite backend instead of only local IndexedDB.

Server (@pubscript/server):
- db.ts: better-sqlite3 schema + migrations (users, shares, projects, books,
  chapters, entities, boards, ai_sessions, audit); WAL mode; idempotent
  admin bootstrap via PUBSCRIPT_ADMIN_EMAIL/PASSWORD.
- auth.ts: argon2 hashing, JWT-ish session tokens, guards, auth routes.
- routes.ts: REST CRUD for projects/books/chapters/entities/boards/ai_sessions
  with multi-tenant isolation and optimistic concurrency (baseRev).
- ws.ts: Fastify websocket hub for autosave + presence events.
- mapping.ts: row <-> core type conversion.

Core (@pubscript/core):
- Zod domain schemas (projects, books, chapters, entities, boards, ai_sessions)
  exported from index.
- storage-local.ts (IndexedDB/Dexie) and storage-server.ts (REST) adapters
  implementing the StorageAdapter contract.

Tests & tooling:
- storage.contract.test.ts: parameterized over both adapters; wired as
  `pnpm contract` and added to CI.
- seed.ts (`pnpm --filter server seed`): creates demo project "The Glass Harbor"
  — 3 chapters of prose, 4 linked characters, 1 world location, 6-node board.
- Dockerfile + compose wiring for the server runtime.

Acceptance: seed project opens with 3 chapters, 4 linked characters, 1 board.

packages/core/src/schema.test.ts

@@ -0,0 +1,23 @@
+import { describe, it, expect } from "vitest";
+import { ENTITY_FIELDS, ENTITY_KINDS } from "./schema.js";
+
+describe("schema ENTITY_FIELDS", () => {
+  it("covers every entity kind from PLAN.md §3.3", () => {
+    for (const kind of ["character", "location", "faction", "item", "glossary", "system", "note"]) {
+      expect(ENTITY_FIELDS[kind]).toBeDefined();
+      expect(ENTITY_FIELDS[kind]!.fields.length).toBeGreaterThan(0);
+    }
+  });
+
+  it("includes a list field and a select field", () => {
+    const character = ENTITY_FIELDS.character;
+    expect(character).toBeDefined();
+    expect(character!.fields.some((f) => f.type === "list")).toBe(true);
+    expect(character!.fields.some((f) => f.type === "select")).toBe(true);
+  });
+
+  it("exposes a stable, ordered kind list", () => {
+    expect(ENTITY_KINDS).toContain("character");
+    expect(ENTITY_KINDS.length).toBeGreaterThanOrEqual(7);
+  });
+});