Initial scaffold — NASBackup iOS app

Full project scaffold: XcodeGen project.yml, Core models/protocols/errors,
SMBService (kishikawakatsumi/SMBClient), SFTPService (Citadel 0.9.2),
PhotoLibraryService, LANMonitor, BackupEngine, BackgroundTaskManager,
all feature UIs (Login, Connect, Browse, Backup, History, Settings),
Shared components and theme. Builds clean with zero errors.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Assets.xcassets/Contents.json

@@ -0,0 +1,6 @@
+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}