Add EXIF auto-orient and aspect ratio lock toggle

- Implement auto_orient_from_exif() that reads EXIF Orientation tag
  and applies the correct rotation/flip for all 8 EXIF orientations
- Add aspect ratio lock toggle to resize step Width/Height mode
- When lock is active, changing width auto-calculates height from
  the first loaded image's aspect ratio, and vice versa
- Uses recursive update guard (Cell<bool>) to prevent infinite loops

pixstrip-core/src/executor.rs

@@ -331,7 +331,7 @@ impl PipelineExecutor {
                 Rotation::Cw90 => img.rotate90(),
                 Rotation::Cw180 => img.rotate180(),
                 Rotation::Cw270 => img.rotate270(),
-                Rotation::AutoOrient => img,
+                Rotation::AutoOrient => auto_orient_from_exif(img, &source.path),
             };
         }
 
@@ -502,6 +502,49 @@ fn num_cpus() -> usize {
         .unwrap_or(1)
 }
 
+/// Read EXIF orientation tag and apply the appropriate rotation/flip.
+/// EXIF orientation values:
+/// 1 = Normal, 2 = Flipped horizontal, 3 = Rotated 180,
+/// 4 = Flipped vertical, 5 = Transposed (flip H + rotate 270),
+/// 6 = Rotated 90 CW, 7 = Transverse (flip H + rotate 90),
+/// 8 = Rotated 270 CW
+fn auto_orient_from_exif(
+    img: image::DynamicImage,
+    path: &std::path::Path,
+) -> image::DynamicImage {
+    let Ok(metadata) = little_exif::metadata::Metadata::new_from_path(path) else {
+        return img;
+    };
+
+    let endian = metadata.get_endian();
+    let Some(tag) = metadata.get_tag(&little_exif::exif_tag::ExifTag::Orientation(Vec::new())) else {
+        return img;
+    };
+
+    let bytes = tag.value_as_u8_vec(endian);
+    if bytes.len() < 2 {
+        return img;
+    }
+
+    // Orientation is a 16-bit unsigned integer
+    let orientation = match endian {
+        little_exif::endian::Endian::Little => u16::from_le_bytes([bytes[0], bytes[1]]),
+        little_exif::endian::Endian::Big => u16::from_be_bytes([bytes[0], bytes[1]]),
+    };
+
+    match orientation {
+        1 => img,                                          // Normal
+        2 => img.fliph(),                                  // Flipped horizontal
+        3 => img.rotate180(),                              // Rotated 180
+        4 => img.flipv(),                                  // Flipped vertical
+        5 => img.fliph().rotate270(),                      // Transposed
+        6 => img.rotate90(),                               // Rotated 90 CW
+        7 => img.fliph().rotate90(),                       // Transverse
+        8 => img.rotate270(),                              // Rotated 270 CW
+        _ => img,
+    }
+}
+
 fn find_unique_path(path: &std::path::Path) -> std::path::PathBuf {
     let stem = path
         .file_stem()