Dingtian input HTTP-push to backend (no polling)

The device pushes button events to the backend via its Input Link URL feature;
the backend decides. No polling — the chosen entry architecture.

packages/devices:
- dingtian driver: configureInputPush() writes the device's input_link_url
  config (per-input server/port/path, en=1, active-LOW, plain HTTP) so each
  input HTTP-GETs the backend on press/release. Extracted #readConfig/#writeConfig
  (with the required command:setconfig injection + post-write reset tolerance).

apps/server:
- routes/devices.ts: public GET/POST
  /api/devices/dingtian/:deviceId/input/:n/{on,off} — translates a device push
  into an internal device event. Not behind cookie/CSRF (machine call from the
  device); trust comes from the signed event log, not this request.
- device-events.ts: internal EventEmitter bus so the entry flow subscribes to
  input events without coupling to HTTP. Wired into the server.

Verified on hardware: configured the device, then real presses on all 4 inputs
pushed to the backend (input N on+off, source = device IP). No polling.

wiki: device-input-flow concept (path + trust model for the flat/no-VLAN
network); dingtian-relay updated; index + log.

apps/server/src/device-events.ts

@@ -0,0 +1,28 @@
+import { EventEmitter } from "node:events";
+
+// Internal event bus for device-originated events (button presses, etc.).
+// Hardware drivers / inbound device pushes emit here; business logic (entry
+// flow, event-log) subscribes — keeping the HTTP/transport layer thin and the
+// app device-agnostic. See wiki/entities/fastify.md.
+
+export interface DeviceInputEvent {
+  readonly driverId: string; // e.g. "dingtian"
+  readonly deviceId: string; // which configured device (lane_devices id)
+  readonly input: number; // 1-based input/channel
+  readonly edge: "on" | "off"; // active / inactive
+  readonly at: string; // ISO-8601 (server receive time)
+  readonly source: "push" | "poll";
+}
+
+class DeviceEventBus extends EventEmitter {
+  emitInput(event: DeviceInputEvent): void {
+    this.emit("input", event);
+  }
+  onInput(cb: (event: DeviceInputEvent) => void): () => void {
+    this.on("input", cb);
+    return () => this.off("input", cb);
+  }
+}
+
+/** Process-wide device event bus. */
+export const deviceEvents = new DeviceEventBus();