Add the Android app: Gradle build, Oboe audio, connection screen

android/ builds core and ts3j from the same sources as the desktop's
Maven build, so the app shares all of the client's logic:

- audio: Oboe streams behind AudioCapture/AudioPlayback, with a lock-free
  ring between the real-time callback and the blocking Java side, and
  libopus 1.5.2 built with the NDK behind OpusCodec. Speakers are mixed
  onto one stream. Capture uses the VoiceRecognition preset, leaving
  noise suppression and gain to the client's own processing.
- app: a plain connection screen to try the port out - connect,
  microphone, mute, deafen, channel chat and a log - until the real UI.

Targets Android 13 and up (minSdk 33) on arm64 and x86_64.

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

android/gradlew.bat

@@ -0,0 +1,112 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+@rem SPDX-License-Identifier: Apache-2.0
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  gradlew startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables, and ensure extensions are enabled
+setlocal EnableExtensions
+
+@rem Catch executions from older scripts and ensure they exit cleanly.
+@rem This can be removed once we can be reasonably confident that few people
+@rem will be migrating directly to this new wrapper.
+goto afterSafetyNet
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
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+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
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+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+goto exitWithErrorLevel
+:afterSafetyNet
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+1>&2 echo.
+1>&2 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+1>&2 echo.
+1>&2 echo Please set the JAVA_HOME variable in your environment to match the
+1>&2 echo location of your Java installation.
+
+"%COMSPEC%" /c exit 1
+goto exitWithErrorLevel
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+1>&2 echo.
+1>&2 echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+1>&2 echo.
+1>&2 echo Please set the JAVA_HOME variable in your environment to match the
+1>&2 echo location of your Java installation.
+
+"%COMSPEC%" /c exit 1
+goto exitWithErrorLevel
+
+:execute
+@rem Setup the command line
+
+
+
+@rem Execute gradlew
+@rem endlocal doesn't take effect until after the line is parsed and variables are expanded
+@rem which allows us to clear the local environment before executing the java command
+endlocal & "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %* & call :exitWithErrorLevel & goto exitWithErrorLevel
+
+@rem This label must not be changed. We rely on old scripts being able to jump to this point.
+:exitWithErrorLevel
+@rem Use "%COMSPEC%" /c exit to allow operators to work properly in scripts
+"%COMSPEC%" /c exit %ERRORLEVEL%