✨ feat: introduce platform-specific BLE backends

solves lack of Linux support in #2

src/lib/ble/backend.ts

@@ -0,0 +1,51 @@
+export interface DiscoveredDevice {
+  address: string;
+  name: string | null;
+}
+
+export interface BleCharacteristic {
+  uuid: string;
+  write(data: Buffer, withoutResponse: boolean): Promise<void>;
+  subscribe(onData: (data: Buffer) => void): Promise<void>;
+  unsubscribe(): Promise<void>;
+}
+
+export interface BleBackend {
+  readonly name: string;
+
+  init(): Promise<void>;
+
+  scanFor(
+    matcher: (device: DiscoveredDevice) => boolean,
+    timeoutMs: number,
+  ): Promise<DiscoveredDevice | null>;
+
+  stopScan(): Promise<void>;
+
+  connect(address: string): Promise<void>;
+
+  onDisconnect(callback: () => void): void;
+
+  discoverCharacteristics(
+    writeUUID: string,
+    notifyUUID: string,
+    normalizeUUID: (uuid: string) => string,
+  ): Promise<{ write: BleCharacteristic; notify: BleCharacteristic }>;
+
+  disconnect(): Promise<void>;
+}
+
+export type BleBackendType = "noble" | "dbus";
+
+/**
+ * Uses dbus on Linux and noble on other platforms.
+ * You can override with BEAMBOXCTL_BLE_BACKEND=noble|dbus.
+ */
+export function resolveBackendType(): BleBackendType {
+  const override = process.env.BEAMBOXCTL_BLE_BACKEND?.toLowerCase().trim();
+  if (override === "noble" || override === "dbus") {
+    return override;
+  }
+
+  return process.platform === "linux" ? "dbus" : "noble";
+}