Add equivalent iOS implementations for PDF feature

https://github.com/google/ground-android/blob/2c40f7a669512d46b72474a1022afe0901d1c7d4/feature/pdf/src/androidMain/kotlin/org/groundplatform/feature/pdf/AndroidPdfReportLauncher.kt#L24-L25

```kotlin

/*
* Copyright 2026 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.groundplatform.feature.pdf

import android.content.Context
import android.content.Intent
import androidx.core.content.FileProvider
import java.io.File

/** Launches the system share sheet or external viewer for a report file via [FileProvider]. */
// TODO: Add equivalent iOS implementations for PDF feature
// Issue URL: https://github.com/google/ground-android/issues/3775
class AndroidPdfReportLauncher(
private val context: Context,
private val fileProviderAuthority: String,
) : PdfReportLauncher {

override fun share(path: String) {
val uri = FileProvider.getUriForFile(context, fileProviderAuthority, File(path))
val sendIntent =
Intent(Intent.ACTION_SEND).apply {
type = PDF_MIME_TYPE
putExtra(Intent.EXTRA_STREAM, uri)
addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
}
launchChooser(sendIntent)
}

override fun open(path: String) {
val uri = FileProvider.getUriForFile(context, fileProviderAuthority, File(path))
val viewIntent =
Intent(Intent.ACTION_VIEW).apply {
setDataAndType(uri, PDF_MIME_TYPE)
addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
}
launchChooser(viewIntent)
}

private fun launchChooser(target: Intent) {
val chooser =
Intent.createChooser(target, null).apply { addFlags(Intent.FLAG_ACTIVITY_NEW_TASK) }
context.startActivity(chooser)
}

companion object {
private const val PDF_MIME_TYPE = "application/pdf"
}
}

```