Append-only signed event log; persist Dingtian input pushes

Implement the core anti-fraud primitive: an append-only, hash-chained,
signed event log (the schema + types predated this; the writer/signer are new).

- EventLog (apps/server): serialized append, monotonic index, prevHash chain,
  signature; verifyChain() detects tamper/reorder/delete. No update/delete paths.
- Signer abstraction (packages/shared) over the ATECC608 secure element, with a
  SoftwareSigner (HMAC, EVENT_SIGNING_KEY) shipped now since the chip is still
  open-question #6. Documented: software signer is tamper-evident but NOT
  unforgeable-by-owner.
- Add ParkingEventType "input_received" for raw device inputs (not yet a
  vehicle_entry, which the entry flow will append later).
- Read API: GET /api/events; integrity self-check: GET /api/events/verify (admin).

Verified on hardware: shorting the Dingtian inputs produced signed, chained
input_received events; verifyChain ok; direct DB tamper/delete detected.

NOTE: the log captures host-originated actions only. Out-of-band relay
actuation (sniffed relay_pw, string protocol, ip_watchdog) produces no event
by design -- the control is reconciliation vs. an independent witness, which is
not yet built. See wiki/concepts/append-only-event-chain.md.

apps/server/src/routes/events.ts

@@ -0,0 +1,38 @@
+import type { FastifyInstance } from "fastify";
+import { desc, events, type Db } from "@parking/db";
+import { requireRole } from "../auth.js";
+import type { EventLog } from "../event-log.js";
+
+// Read access to the append-only signed event log. NO write/update/delete routes
+// exist by design — events are only ever appended internally (entry flow, device
+// pushes). Corrections are new appended events, never edits. See
+// wiki/concepts/append-only-event-chain.md.
+
+export async function eventRoutes(
+  app: FastifyInstance,
+  db: Db,
+  eventLog: EventLog,
+): Promise<void> {
+  // Any authenticated role may read the log (it's the audit trail).
+  const guard = requireRole("admin", "operator", "cashier", "readonly");
+
+  // Recent events, newest first. `limit` caps the page (default 100, max 1000).
+  app.get<{ Querystring: { limit?: string } }>(
+    "/api/events",
+    { preHandler: guard },
+    async (req) => {
+      const limit = Math.min(Math.max(Number(req.query.limit) || 100, 1), 1000);
+      const rows = db.select().from(events).orderBy(desc(events.index)).limit(limit).all();
+      return { events: rows };
+    },
+  );
+
+  // Integrity self-check: walk the chain and verify hashes + signatures. Admin-
+  // only (it's an audit action). Returns the first break, or ok. This is what a
+  // reconciliation job / "is the log intact?" check calls.
+  app.get(
+    "/api/events/verify",
+    { preHandler: requireRole("admin") },
+    async () => eventLog.verifyChain(),
+  );
+}