feat: apply EXIF orientation and colorspace correction to ffmpeg thumbnails

HEIC/HEIF sources use Display P3 color primaries. Without
colorspace=bt709 the mjpeg encoder treated P3 values as sRGB,
producing warm/oversaturated output. Also bake EXIF Orientation
tag into pixels so saved JPEGs are canonically oriented.

- Extract orientation from exif-reader and pass through all
  ffmpeg thumbnail paths (small, large, xlarge previews)
- Add shared build_image_thumb_filter() for the 200px path
- Add rotation + colorspace=bt709 to large/xlarge ffmpeg paths

src/video/actors.rs

@@ -90,10 +90,39 @@ pub fn generate_video_thumbnail(path: &Path, destination: &Path) -> std::io::Res
     Ok(())
 }
 
-/// Use ffmpeg to extract a 200px-wide thumbnail from formats the `image` crate
-/// can't decode (RAW: NEF/ARW, HEIC/HEIF). Writes JPEG bytes to `destination`
-/// regardless of its extension.
-pub fn generate_image_thumbnail_ffmpeg(path: &Path, destination: &Path) -> std::io::Result<()> {
+/// Build the ffmpeg filter chain for image thumbnails: rotation (from EXIF
+/// orientation) + scale + color-space conversion. HEIC sources use Display P3
+/// primaries; without `colorspace=bt709` the mjpeg encoder treats P3 values
+/// as sRGB, producing warm/oversaturated output.
+fn build_image_thumb_filter(orientation: i32, scale_w: u32) -> String {
+    let rotation = match orientation {
+        2 => "hflip",
+        3 => "transpose=2",
+        4 => "vflip",
+        5 => "transpose=0,hflip",
+        6 => "transpose=0",
+        7 => "transpose=1,hflip",
+        8 => "transpose=1",
+        _ => "", // orientation 1 or unknown — no rotation needed
+    };
+    if rotation.is_empty() {
+        format!("scale={}:{{-1}},colorspace=bt709", scale_w)
+    } else {
+        format!("{},scale={}:{{-1}},colorspace=bt709", rotation, scale_w)
+    }
+}
+
+/// Use ffmpeg to extract a thumbnail from formats the `image` crate can't
+/// decode (HEIC/HEIF, RAW: NEF/ARW). `orientation` is the EXIF Orientation
+/// tag value (1..=8) — baked into the pixels so the saved JPEG is
+/// canonically oriented. Writes JPEG bytes to `destination` regardless of
+/// its extension.
+pub fn generate_image_thumbnail_ffmpeg(
+    path: &Path,
+    destination: &Path,
+    orientation: i32,
+) -> std::io::Result<()> {
+    let vf = build_image_thumb_filter(orientation, 200);
     let output = Command::new("ffmpeg")
         .arg("-y")
         .arg("-i")
@@ -101,7 +130,7 @@ pub fn generate_image_thumbnail_ffmpeg(path: &Path, destination: &Path) -> std::
         .arg("-vframes")
         .arg("1")
         .arg("-vf")
-        .arg("scale=200:-1")
+        .arg(&vf)
         .arg("-f")
         .arg("image2")
         .arg("-c:v")