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.

wiki/concepts/append-only-event-chain.md

@@ -0,0 +1,26 @@
+---
+type: concept
+tags: [parking, security, integrity]
+sources: [parking-system-architecture]
+updated: 2026-06-14
+---
+
+# Append-Only Event Chain
+
+The core integrity mechanism against operator fraud (see [[threat-model]]). (See
+[[parking-system-architecture]] §3.)
+
+Three layered properties:
+
+1. **Append-only event model.** Entry/exit events are never edited or deleted, only appended. A
+   "void" is itself a **recorded event**, not an erasure.
+2. **Tamper-evident chaining.** Each event stores the **hash of the previous event** (a hash
+   chain). Reordering or deleting **breaks the chain visibly**.
+3. **Hardware-backed signing.** The **[[atecc608]]** secure element signs each event with a
+   non-extractable key. This is what makes the chain **unforgeable** rather than merely
+   self-consistent — someone who owns the machine still cannot forge a valid entry.
+
+It only becomes trustworthy as an external fraud control when paired with [[reconciliation]]
+against an authority the operator can't alter. Every device event — including those ingested
+from the [[uhppote-controller]] via [[event-log-ingestion]] — should land in this host-side
+chain.