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/theme.ts

@@ -0,0 +1,132 @@
+/**
+ * Theme engine — CSS-variable token map. See PLAN.md §4.7 and CHUNK #1 step 3.
+ *
+ * Four themes ship as token objects; `applyTheme(id)` sets
+ * `document.documentElement.dataset.theme`. Accent color and density are
+ * runtime overrides layered on top.
+ */
+
+export type ThemeId = "ink" | "parchment" | "nocturne" | "terminal";
+
+export const THEME_IDS: ThemeId[] = ["ink", "parchment", "nocturne", "terminal"];
+
+export const THEME_LABELS: Record<ThemeId, string> = {
+  ink: "Ink",
+  parchment: "Parchment",
+  nocturne: "Nocturne",
+  terminal: "Terminal",
+};
+
+export interface ThemeTokens {
+  label: string;
+  /** CSS custom properties applied to :root when this theme is active. */
+  css: Record<string, string>;
+}
+
+/**
+ * The four themes. Ink is the default (dark). Parchment is warm light,
+ * Nocturne is deep indigo, Terminal is monochrome monospace.
+ */
+export const THEME_TOKENS: Record<ThemeId, ThemeTokens> = {
+  ink: {
+    label: "Ink",
+    css: {
+      "--ps-bg": "#0e0f13",
+      "--ps-surface": "#17181f",
+      "--ps-surface-2": "#20222c",
+      "--ps-border": "#2a2d3a",
+      "--ps-text": "#e6e8ee",
+      "--ps-text-muted": "#9aa0b0",
+      "--ps-accent": "#7c8bf5",
+      "--ps-accent-contrast": "#0e0f13",
+      "--ps-danger": "#f16d7a",
+      "--ps-success": "#5fd08a",
+      "--ps-warning": "#f0b754",
+    },
+  },
+  parchment: {
+    label: "Parchment",
+    css: {
+      "--ps-bg": "#f6f1e7",
+      "--ps-surface": "#fffdf7",
+      "--ps-surface-2": "#f2ead8",
+      "--ps-border": "#e2d6bd",
+      "--ps-text": "#2c2720",
+      "--ps-text-muted": "#6f6656",
+      "--ps-accent": "#b5793a",
+      "--ps-accent-contrast": "#fffdf7",
+      "--ps-danger": "#c0392b",
+      "--ps-success": "#2e7d4f",
+      "--ps-warning": "#b8860b",
+    },
+  },
+  nocturne: {
+    label: "Nocturne",
+    css: {
+      "--ps-bg": "#0c0b1e",
+      "--ps-surface": "#171533",
+      "--ps-surface-2": "#221f4a",
+      "--ps-border": "#2e2a5e",
+      "--ps-text": "#e8e6ff",
+      "--ps-text-muted": "#a49fcf",
+      "--ps-accent": "#9d7bff",
+      "--ps-accent-contrast": "#0c0b1e",
+      "--ps-danger": "#ff7b9c",
+      "--ps-success": "#6ee7a8",
+      "--ps-warning": "#ffd27b",
+    },
+  },
+  terminal: {
+    label: "Terminal",
+    css: {
+      "--ps-bg": "#05070a",
+      "--ps-surface": "#0a0f14",
+      "--ps-surface-2": "#0f1720",
+      "--ps-border": "#16232e",
+      "--ps-text": "#33ff9b",
+      "--ps-text-muted": "#2c8a63",
+      "--ps-accent": "#33ff9b",
+      "--ps-accent-contrast": "#05070a",
+      "--ps-danger": "#ff6b6b",
+      "--ps-success": "#33ff9b",
+      "--ps-warning": "#ffd93d",
+    },
+  },
+};
+
+/** The active theme id, persisted by the settings store. */
+let activeTheme: ThemeId = "ink";
+
+/** Return the token map for a theme id (throws on unknown). */
+export function getThemeTokens(id: ThemeId): ThemeTokens {
+  const t = THEME_TOKENS[id];
+  if (!t) {
+    throw new Error(`Unknown theme: ${id}`);
+  }
+  return t;
+}
+
+/**
+ * Apply a theme by setting the data attribute and writing its CSS variables to
+ * :root. Returns the applied id. Safe to call before the DOM exists (no-op).
+ */
+export function applyTheme(id: ThemeId): ThemeId {
+  if (!THEME_TOKENS[id]) {
+    throw new Error(`Unknown theme: ${id}`);
+  }
+  activeTheme = id;
+  const root = typeof document !== "undefined" ? document.documentElement : undefined;
+  if (root) {
+    root.dataset.theme = id;
+    const { css } = THEME_TOKENS[id]!;
+    for (const [k, v] of Object.entries(css)) {
+      root.style.setProperty(k, v);
+    }
+  }
+  return id;
+}
+
+/** The currently active theme id. */
+export function getActiveTheme(): ThemeId {
+  return activeTheme;
+}