fix(resources): grant explicit URI permissions to all resolved activities before startActivity

Resolves 'Keine App gefunden' for ePub and PDF opening failures (e.g. Firefox).
FLAG_GRANT_READ_URI_PERMISSION alone is not sufficient when Android shows
the Chooser – each potential app must receive grantUriPermission() before
startActivity() is called.

- Extract openResourceFile() into FileOpenHelper.kt (eliminates DRY violation)
- Use PackageManager.ResolveInfoFlags (API 33+) with DEPRECATION suppress fallback
- Remove duplicate inline intent code from ResourceDetailScreen

Closes #129

app/src/main/java/de/bollwerk/app/ui/resources/FileOpenHelper.kt

@@ -0,0 +1,55 @@
+package de.bollwerk.app.ui.resources
+
+import android.content.ActivityNotFoundException
+import android.content.Context
+import android.content.Intent
+import android.content.pm.PackageManager
+import android.os.Build
+import androidx.compose.material3.SnackbarHostState
+import androidx.core.content.FileProvider
+import java.io.File
+
+/**
+ * Öffnet eine Ressourcen-Datei in einer externen App via FileProvider.
+ *
+ * Erteilt vor dem `startActivity`-Aufruf explizit URI-Berechtigungen an alle Apps,
+ * die den Intent auflösen können – notwendig damit der Android-Chooser die Berechtigung
+ * korrekt weitergibt (z.B. Firefox für PDFs).
+ */
+internal suspend fun openResourceFile(
+    context: Context,
+    file: File,
+    mimeType: String,
+    snackbarHostState: SnackbarHostState
+) {
+    val uri = FileProvider.getUriForFile(context, "${context.packageName}.fileprovider", file)
+    val intent = Intent(Intent.ACTION_VIEW).apply {
+        setDataAndType(uri, mimeType)
+        addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+    }
+
+    // Explizit URI-Berechtigung an alle Apps vergeben, die diesen Intent auflösen können,
+    // damit der Android-Chooser die Berechtigung korrekt weitergibt (z.B. Firefox für PDFs).
+    val resolvedActivities = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+        context.packageManager.queryIntentActivities(
+            intent,
+            PackageManager.ResolveInfoFlags.of(PackageManager.MATCH_DEFAULT_ONLY.toLong())
+        )
+    } else {
+        @Suppress("DEPRECATION")
+        context.packageManager.queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY)
+    }
+    resolvedActivities.forEach { resolveInfo ->
+        context.grantUriPermission(
+            resolveInfo.activityInfo.packageName,
+            uri,
+            Intent.FLAG_GRANT_READ_URI_PERMISSION
+        )
+    }
+
+    try {
+        context.startActivity(intent)
+    } catch (_: ActivityNotFoundException) {
+        snackbarHostState.showSnackbar("Keine App zum Öffnen dieser Datei gefunden")
+    }
+}

app/src/main/java/de/bollwerk/app/ui/resources/ResourceDetailScreen.kt

@@ -1,7 +1,5 @@
 package de.bollwerk.app.ui.resources
 
-import android.content.ActivityNotFoundException
-import android.content.Intent
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.ExperimentalLayoutApi
@@ -42,7 +40,6 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
-import androidx.core.content.FileProvider
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import de.bollwerk.shared.model.ResourceDto
@@ -67,16 +64,7 @@ internal fun ResourceDetailScreen(
     // Handle download success
     if (downloadState is DownloadState.Success) {
         LaunchedEffect(downloadState) {
-            val uri = FileProvider.getUriForFile(context, "${context.packageName}.fileprovider", downloadState.file)
+            openResourceFile(context, downloadState.file, downloadState.mimeType, snackbarHostState)
-            val intent = Intent(Intent.ACTION_VIEW).apply {
-                setDataAndType(uri, downloadState.mimeType)
-                addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
-            }
-            try {
-                context.startActivity(intent)
-            } catch (_: ActivityNotFoundException) {
-                snackbarHostState.showSnackbar("Keine App zum Öffnen dieser Datei gefunden")
-            }
             viewModel.clearDownloadState(guid)
         }
     }

app/src/main/java/de/bollwerk/app/ui/resources/ResourceListScreen.kt

@@ -1,8 +1,5 @@
 package de.bollwerk.app.ui.resources
 
-import android.content.ActivityNotFoundException
-import android.content.Context
-import android.content.Intent
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -61,7 +58,6 @@ import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.semantics.Role
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
-import androidx.core.content.FileProvider
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import de.bollwerk.shared.model.ResourceDto
@@ -112,7 +108,7 @@ internal fun ResourceListScreen(
         when (state) {
             is DownloadState.Success -> {
                 LaunchedEffect(guid, state) {
-                    openFile(context, state.file, state.mimeType, snackbarHostState)
+                    openResourceFile(context, state.file, state.mimeType, snackbarHostState)
                     viewModel.clearDownloadState(guid)
                 }
             }
@@ -519,20 +515,4 @@ private fun formatFileSize(bytes: Long): String {
     }
 }
 
-private suspend fun openFile(
+
-    context: Context,
-    file: File,
-    mimeType: String,
-    snackbarHostState: SnackbarHostState
-) {
-    val uri = FileProvider.getUriForFile(context, "${context.packageName}.fileprovider", file)
-    val intent = Intent(Intent.ACTION_VIEW).apply {
-        setDataAndType(uri, mimeType)
-        addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
-    }
-    try {
-        context.startActivity(intent)
-    } catch (_: ActivityNotFoundException) {
-        snackbarHostState.showSnackbar("Keine App zum Öffnen dieser Datei gefunden")
-    }
-}