Initial scaffold: Turborepo monorepo + design wiki

Turborepo (pnpm workspaces) with all dependencies pinned to latest
mutually-compatible versions: turbo 2.9, TypeScript 6, Fastify 5,
React 19, Vite 8, better-sqlite3 12 + Drizzle ORM 0.45.

Layout:
- apps/server   Fastify backend (local JWT auth + role guard, /health)
- apps/web      React 19 + Vite 8 operator SPA
- packages/db   Drizzle schema on SQLite/WAL; append-only events + users
- packages/devices  reader/printer/relay adapter interfaces (intent-only relay)
- packages/shared   shared domain types

Architecture constraints from the design wiki are encoded in the scaffold:
append-only hash-chained + signed event log, device-agnostic adapters,
"a barrier is not a door" (relay expresses intent only), fully-local
offline-first auth.

wiki/ is an LLM-maintained Obsidian knowledge base (28 pages) ingested
from the architecture & design notes, with its own maintenance schema.

Verified: pnpm install, full turbo build (5/5), server boots and serves
/health, drizzle-kit generates the initial migration.

packages/shared/src/index.ts

@@ -0,0 +1,50 @@
+// Shared types and utilities across the parking system.
+//
+// The domain is offline-first and threat-model driven. The central integrity
+// primitive is an append-only, hash-chained, ATECC608-signed event log: entry
+// and exit events are never edited or deleted — a "void" is itself an appended
+// event. See wiki/concepts/append-only-event-chain.md.
+
+export type Role = "admin" | "operator" | "cashier" | "readonly";
+
+export type Direction = "entry" | "exit";
+
+/** What kind of identity source produced a read. */
+export type IdentitySource = "wiegand" | "lpr" | "qr" | "ticket" | "manual";
+
+/**
+ * An append-only parking event. Records are never mutated; corrections are new
+ * events. `prevHash` chains each event to the previous one; `signature` is the
+ * ATECC608 signature over the event contents. See wiki/append-only-event-chain.
+ */
+export interface ParkingEvent {
+  readonly id: string;
+  readonly index: number;
+  readonly type: ParkingEventType;
+  readonly direction: Direction | null;
+  readonly lane: number;
+  readonly source: IdentitySource | null;
+  /** Card number, plate, ticket id, etc. — depends on `source`. */
+  readonly identity: string | null;
+  readonly occurredAt: string; // ISO-8601
+  /** Hash of the previous event in the chain (hex). Null only for genesis. */
+  readonly prevHash: string | null;
+  /** ATECC608 signature over the canonical event payload (hex). */
+  readonly signature: string;
+}
+
+export type ParkingEventType =
+  | "vehicle_entry"
+  | "vehicle_exit"
+  | "void"
+  | "barrier_open_command"
+  | "barrier_open_observed"
+  | "shift_z_report"
+  | "anomaly";
+
+export const ROLES: readonly Role[] = [
+  "admin",
+  "operator",
+  "cashier",
+  "readonly",
+] as const;