Wire progressive JPEG, AVIF speed, and custom per-format quality to encoder

- Add EncoderOptions struct with progressive_jpeg and avif_speed fields
- Pass encoder options through ProcessingJob to PipelineExecutor
- mozjpeg set_progressive_mode() called when progressive JPEG enabled
- AVIF encoder speed now configurable (was hardcoded to 6)
- run_processing uses CompressConfig::Custom when user overrides preset defaults
- Executor properly handles AVIF quality and PNG level in Custom mode

pixstrip-gtk/src/app.rs

@@ -1265,9 +1265,31 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
     }
 
     if cfg.compress_enabled {
-        job.compress = Some(pixstrip_core::operations::CompressConfig::Preset(cfg.quality_preset));
+        // Check if user has customized per-format quality values beyond the preset defaults
+        let preset_jpeg = cfg.quality_preset.jpeg_quality();
+        let preset_webp = cfg.quality_preset.webp_quality();
+        let has_custom = cfg.jpeg_quality != preset_jpeg
+            || cfg.webp_quality != preset_webp as u8
+            || cfg.avif_quality != preset_webp as u8
+            || cfg.avif_speed != 6
+            || cfg.webp_effort != 4;
+
+        if has_custom {
+            job.compress = Some(pixstrip_core::operations::CompressConfig::Custom {
+                jpeg_quality: Some(cfg.jpeg_quality),
+                png_level: Some(cfg.png_level),
+                webp_quality: Some(cfg.webp_quality as f32),
+                avif_quality: Some(cfg.avif_quality as f32),
+            });
+        } else {
+            job.compress = Some(pixstrip_core::operations::CompressConfig::Preset(cfg.quality_preset));
+        }
     }
 
+    // Pass encoder options to the job
+    job.progressive_jpeg = cfg.progressive_jpeg;
+    job.avif_speed = cfg.avif_speed;
+
     if cfg.metadata_enabled {
         job.metadata = Some(match cfg.metadata_mode {
             MetadataMode::StripAll => pixstrip_core::operations::MetadataConfig::StripAll,