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.

server/src/migrations/001_initial.sql

@@ -0,0 +1,101 @@
+-- 001_initial.sql — the full PubScript schema (CHUNK #2 step 2).
+-- Applied in filename order; tracked in `schema_migrations`.
+
+CREATE TABLE IF NOT EXISTS users (
+  id           TEXT PRIMARY KEY,
+  email        TEXT UNIQUE NOT NULL,
+  pass_hash    TEXT NOT NULL,
+  display_name TEXT NOT NULL,
+  role         TEXT NOT NULL DEFAULT 'author' CHECK (role IN ('admin', 'author')),
+  disabled     INTEGER NOT NULL DEFAULT 0,
+  created_at   TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS sessions (
+  token_hash TEXT PRIMARY KEY,
+  user_id    TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  expires_at TEXT NOT NULL,
+  created_at TEXT NOT NULL
+);
+CREATE INDEX IF NOT EXISTS idx_sessions_user ON sessions(user_id);
+
+CREATE TABLE IF NOT EXISTS projects (
+  id         TEXT PRIMARY KEY,
+  owner_id   TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  title      TEXT NOT NULL,
+  settings   TEXT NOT NULL DEFAULT '{}',
+  cover      TEXT NOT NULL DEFAULT '{}',
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL
+);
+CREATE INDEX IF NOT EXISTS idx_projects_owner ON projects(owner_id);
+
+CREATE TABLE IF NOT EXISTS project_shares (
+  project_id TEXT NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
+  user_id    TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  perm       TEXT NOT NULL CHECK (perm IN ('read', 'edit')),
+  PRIMARY KEY (project_id, user_id)
+);
+
+CREATE TABLE IF NOT EXISTS books (
+  id         TEXT PRIMARY KEY,
+  project_id TEXT NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
+  title      TEXT NOT NULL,
+  ord        INTEGER NOT NULL DEFAULT 0
+);
+CREATE INDEX IF NOT EXISTS idx_books_project ON books(project_id);
+
+CREATE TABLE IF NOT EXISTS chapters (
+  id         TEXT PRIMARY KEY,
+  book_id    TEXT NOT NULL REFERENCES books(id) ON DELETE CASCADE,
+  project_id TEXT NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
+  title      TEXT NOT NULL,
+  doc        TEXT NOT NULL DEFAULT '{"type":"doc","content":[]}',
+  rev        INTEGER NOT NULL DEFAULT 0,
+  ord        INTEGER NOT NULL DEFAULT 0,
+  updated_at TEXT NOT NULL
+);
+CREATE INDEX IF NOT EXISTS idx_chapters_project ON chapters(project_id);
+CREATE INDEX IF NOT EXISTS idx_chapters_book ON chapters(book_id);
+
+CREATE TABLE IF NOT EXISTS entities (
+  id         TEXT NOT NULL,
+  project_id TEXT NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
+  kind       TEXT NOT NULL,
+  name       TEXT NOT NULL,
+  fields     TEXT NOT NULL DEFAULT '{}',
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL,
+  PRIMARY KEY (project_id, kind, id)
+);
+CREATE INDEX IF NOT EXISTS idx_entities_project_kind ON entities(project_id, kind);
+
+CREATE TABLE IF NOT EXISTS boards (
+  id         TEXT PRIMARY KEY,
+  project_id TEXT NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
+  nodes      TEXT NOT NULL DEFAULT '[]',
+  edges      TEXT NOT NULL DEFAULT '[]',
+  updated_at TEXT NOT NULL
+);
+CREATE INDEX IF NOT EXISTS idx_boards_project ON boards(project_id);
+
+CREATE TABLE IF NOT EXISTS ai_sessions (
+  id          TEXT PRIMARY KEY,
+  project_id  TEXT NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
+  role        TEXT NOT NULL,
+  model       TEXT NOT NULL,
+  settings    TEXT NOT NULL DEFAULT '{}',
+  messages    TEXT NOT NULL DEFAULT '[]',
+  suggestions TEXT NOT NULL DEFAULT '[]',
+  updated_at  TEXT NOT NULL
+);
+CREATE INDEX IF NOT EXISTS idx_ai_sessions_project ON ai_sessions(project_id);
+
+CREATE TABLE IF NOT EXISTS audit (
+  id      TEXT PRIMARY KEY,
+  at      TEXT NOT NULL,
+  user_id TEXT,
+  action  TEXT NOT NULL,
+  detail  TEXT NOT NULL DEFAULT '{}'
+);
+CREATE INDEX IF NOT EXISTS idx_audit_at ON audit(at);