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/ui/src/components/Select.tsx

@@ -0,0 +1,25 @@
+import { type SelectHTMLAttributes } from "react";
+
+export interface SelectOption {
+  value: string;
+  label: string;
+}
+
+export interface SelectProps extends SelectHTMLAttributes<HTMLSelectElement> {
+  label?: string;
+  options: SelectOption[];
+}
+
+export function Select({ label, options, id, className = "", ...rest }: SelectProps) {
+  const selectId = id ?? `select-${Math.random().toString(36).slice(2, 8)}`;
+  return (
+    <div className="ps-field">
+      {label && <label htmlFor={selectId} className="ps-field-label">{label}</label>}
+      <select id={selectId} className={`ps-select ${className}`.trim()} {...rest}>
+        {options.map((o) => (
+          <option key={o.value} value={o.value}>{o.label}</option>
+        ))}
+      </select>
+    </div>
+  );
+}