feat(waiter): Capacitor 8 Android project, native build mode, signed APK tooling

- capacitor.config.json: appId gr.bonamin.xenia, webDir dist-native,
  androidScheme http (origin http://localhost - no mixed-content block when
  calling venue servers over plain HTTP on the LAN)
- vite: `--mode native` builds to dist-native with the PWA plugin disabled
  (no service worker inside the app)
- Android: minSdk 24 / target 36; CAMERA permission for QR pairing;
  cleartext allowed via network_security_config (LAN IPs can't be listed
  per-domain); allowBackup=false so backups never carry login tokens
- Release signing reads ~/.xenia/keystore.properties (override with
  XENIA_KEYSTORE_PROPS) - the key never enters the repo; versionName 1.0.0 /
  versionCode 1 with a bump-both rule for sideloaded updates
- npm scripts build:native, apk:debug, apk:release (scripts/build-apk.mjs);
  APKs land in releases/ (gitignored); release APK is also copied to
  public/downloads/ so venue servers serve it at /downloads/xenia-waiter.apk
- waiter nginx: /downloads/ served as application/vnd.android.package-archive,
  real 404 when missing (never falls through to index.html)
- launcher icons + splash generated from the app icon (assets/ is the source)
- .gitattributes: gradlew LF, *.bat CRLF

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

waiter_pwa/android/.gitignore

@@ -0,0 +1,101 @@
+# Using Android gitignore template: https://github.com/github/gitignore/blob/HEAD/Android.gitignore
+
+# Built application files
+*.apk
+*.aar
+*.ap_
+*.aab
+
+# Files for the ART/Dalvik VM
+*.dex
+
+# Java class files
+*.class
+
+# Generated files
+bin/
+gen/
+out/
+#  Uncomment the following line in case you need and you don't have the release build type files in your app
+# release/
+
+# Gradle files
+.gradle/
+build/
+
+# Local configuration file (sdk path, etc)
+local.properties
+
+# Proguard folder generated by Eclipse
+proguard/
+
+# Log Files
+*.log
+
+# Android Studio Navigation editor temp files
+.navigation/
+
+# Android Studio captures folder
+captures/
+
+# IntelliJ
+*.iml
+.idea/workspace.xml
+.idea/tasks.xml
+.idea/gradle.xml
+.idea/assetWizardSettings.xml
+.idea/dictionaries
+.idea/libraries
+# Android Studio 3 in .gitignore file.
+.idea/caches
+.idea/modules.xml
+# Comment next line if keeping position of elements in Navigation Editor is relevant for you
+.idea/navEditor.xml
+
+# Keystore files
+# Uncomment the following lines if you do not want to check your keystore files in.
+#*.jks
+#*.keystore
+
+# External native build folder generated in Android Studio 2.2 and later
+.externalNativeBuild
+.cxx/
+
+# Google Services (e.g. APIs or Firebase)
+# google-services.json
+
+# Freeline
+freeline.py
+freeline/
+freeline_project_description.json
+
+# fastlane
+fastlane/report.xml
+fastlane/Preview.html
+fastlane/screenshots
+fastlane/test_output
+fastlane/readme.md
+
+# Version control
+vcs.xml
+
+# lint
+lint/intermediates/
+lint/generated/
+lint/outputs/
+lint/tmp/
+# lint/reports/
+
+# Android Profiling
+*.hprof
+
+# Cordova plugins for Capacitor
+capacitor-cordova-android-plugins
+
+# Copied web assets
+app/src/main/assets/public
+
+# Generated Config files
+app/src/main/assets/capacitor.config.json
+app/src/main/assets/capacitor.plugins.json
+app/src/main/res/xml/config.xml