Add bottom bar gesture exclusion, dual image save, thumbnail preview, and gallery picker

- Increase bottom padding and add systemGestureExclusion to prevent
  accidental navigation gestures from the capture controls
- Save both original and processed images with shared timestamps
  (TILTSHIFT_* and ORIGINAL_*) via new saveBitmapPair() pipeline
- Show animated thumbnail of last captured photo at bottom-right;
  tap opens the image in the default photo viewer
- Add gallery picker button to process existing photos through the
  tilt-shift pipeline with full EXIF rotation support

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

app/src/main/java/no/naiv/tiltshift/storage/PhotoSaver.kt

@@ -21,7 +21,12 @@ import java.util.Locale
  * Result of a photo save operation.
  */
 sealed class SaveResult {
-    data class Success(val uri: Uri, val path: String) : SaveResult()
+    data class Success(
+        val uri: Uri,
+        val path: String,
+        val originalUri: Uri? = null,
+        val thumbnail: android.graphics.Bitmap? = null
+    ) : SaveResult()
     data class Error(val message: String, val exception: Exception? = null) : SaveResult()
 }
 
@@ -44,10 +49,44 @@ class PhotoSaver(private val context: Context) {
         orientation: Int,
         location: Location?
     ): SaveResult = withContext(Dispatchers.IO) {
-        try {
-            val fileName = "TILTSHIFT_${fileNameFormat.format(Date())}.jpg"
+        val fileName = "TILTSHIFT_${fileNameFormat.format(Date())}.jpg"
+        saveSingleBitmap(fileName, bitmap, orientation, location)
+    }
 
-            // Create content values for MediaStore
+    /**
+     * Saves both original and processed bitmaps to the gallery.
+     * Uses a shared timestamp so paired files sort together.
+     * Returns the processed image's URI as the primary result.
+     */
+    suspend fun saveBitmapPair(
+        original: Bitmap,
+        processed: Bitmap,
+        orientation: Int,
+        location: Location?
+    ): SaveResult = withContext(Dispatchers.IO) {
+        val timestamp = fileNameFormat.format(Date())
+        val processedFileName = "TILTSHIFT_${timestamp}.jpg"
+        val originalFileName = "ORIGINAL_${timestamp}.jpg"
+
+        val processedResult = saveSingleBitmap(processedFileName, processed, orientation, location)
+        if (processedResult is SaveResult.Error) return@withContext processedResult
+
+        val originalResult = saveSingleBitmap(originalFileName, original, orientation, location)
+        val originalUri = (originalResult as? SaveResult.Success)?.uri
+
+        (processedResult as SaveResult.Success).copy(originalUri = originalUri)
+    }
+
+    /**
+     * Core save logic: writes a single bitmap to MediaStore with EXIF data.
+     */
+    private fun saveSingleBitmap(
+        fileName: String,
+        bitmap: Bitmap,
+        orientation: Int,
+        location: Location?
+    ): SaveResult {
+        return try {
             val contentValues = ContentValues().apply {
                 put(MediaStore.Images.Media.DISPLAY_NAME, fileName)
                 put(MediaStore.Images.Media.MIME_TYPE, "image/jpeg")
@@ -57,29 +96,23 @@ class PhotoSaver(private val context: Context) {
                 put(MediaStore.Images.Media.IS_PENDING, 1)
             }
 
-            // Insert into MediaStore
             val contentResolver = context.contentResolver
             val uri = contentResolver.insert(
                 MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                 contentValues
-            ) ?: return@withContext SaveResult.Error("Failed to create MediaStore entry")
+            ) ?: return SaveResult.Error("Failed to create MediaStore entry")
 
-            // Write bitmap to output stream
             contentResolver.openOutputStream(uri)?.use { outputStream ->
                 bitmap.compress(Bitmap.CompressFormat.JPEG, 95, outputStream)
-            } ?: return@withContext SaveResult.Error("Failed to open output stream")
+            } ?: return SaveResult.Error("Failed to open output stream")
 
-            // Write EXIF data
             writeExifToUri(uri, orientation, location)
 
-            // Mark as complete
             contentValues.clear()
             contentValues.put(MediaStore.Images.Media.IS_PENDING, 0)
             contentResolver.update(uri, contentValues, null, null)
 
-            // Get the file path for display
             val path = getPathFromUri(uri)
-
             SaveResult.Success(uri, path)
         } catch (e: Exception) {
             SaveResult.Error("Failed to save photo: ${e.message}", e)