Restore session settings for convert format, quality preset, and metadata mode

- Parse stored format/quality/metadata strings back to enum values on launch
- Remove duplicate help button handler
- Session now properly round-trips all wizard state between launches

pixstrip-gtk/src/app.rs

@@ -169,6 +169,39 @@ fn load_css() {
     );
 }
 
+fn parse_image_format(s: &str) -> Option<pixstrip_core::types::ImageFormat> {
+    match s {
+        "Jpeg" => Some(pixstrip_core::types::ImageFormat::Jpeg),
+        "Png" => Some(pixstrip_core::types::ImageFormat::Png),
+        "WebP" => Some(pixstrip_core::types::ImageFormat::WebP),
+        "Avif" => Some(pixstrip_core::types::ImageFormat::Avif),
+        "Gif" => Some(pixstrip_core::types::ImageFormat::Gif),
+        "Tiff" => Some(pixstrip_core::types::ImageFormat::Tiff),
+        _ => None,
+    }
+}
+
+fn parse_quality_preset(s: &str) -> Option<pixstrip_core::types::QualityPreset> {
+    match s {
+        "Maximum" => Some(pixstrip_core::types::QualityPreset::Maximum),
+        "High" => Some(pixstrip_core::types::QualityPreset::High),
+        "Medium" => Some(pixstrip_core::types::QualityPreset::Medium),
+        "Low" => Some(pixstrip_core::types::QualityPreset::Low),
+        "WebOptimized" => Some(pixstrip_core::types::QualityPreset::WebOptimized),
+        _ => None,
+    }
+}
+
+fn parse_metadata_mode(s: &str) -> Option<MetadataMode> {
+    match s {
+        "StripAll" => Some(MetadataMode::StripAll),
+        "Privacy" => Some(MetadataMode::Privacy),
+        "KeepAll" => Some(MetadataMode::KeepAll),
+        "Custom" => Some(MetadataMode::Custom),
+        _ => None,
+    }
+}
+
 fn build_ui(app: &adw::Application) {
     load_css();
 
@@ -202,14 +235,24 @@ fn build_ui(app: &adw::Application) {
             trim_whitespace: false,
             canvas_padding: 0,
             convert_enabled: if remember { sess_state.convert_enabled.unwrap_or(false) } else { false },
-            convert_format: None,
+            convert_format: if remember {
+                sess_state.convert_format.as_deref().and_then(parse_image_format)
+            } else {
+                None
+            },
             progressive_jpeg: false,
             format_mapping_jpeg: 0,
             format_mapping_png: 0,
             format_mapping_webp: 0,
             format_mapping_tiff: 0,
             compress_enabled: if remember { sess_state.compress_enabled.unwrap_or(true) } else { true },
-            quality_preset: pixstrip_core::types::QualityPreset::Medium,
+            quality_preset: if remember {
+                sess_state.quality_preset.as_deref()
+                    .and_then(parse_quality_preset)
+                    .unwrap_or(pixstrip_core::types::QualityPreset::Medium)
+            } else {
+                pixstrip_core::types::QualityPreset::Medium
+            },
             jpeg_quality: 85,
             png_level: 3,
             webp_quality: 80,
@@ -217,7 +260,13 @@ fn build_ui(app: &adw::Application) {
             webp_effort: 4,
             avif_speed: 6,
             metadata_enabled: if remember { sess_state.metadata_enabled.unwrap_or(true) } else { true },
-            metadata_mode: MetadataMode::StripAll,
+            metadata_mode: if remember {
+                sess_state.metadata_mode.as_deref()
+                    .and_then(parse_metadata_mode)
+                    .unwrap_or(MetadataMode::StripAll)
+            } else {
+                MetadataMode::StripAll
+            },
             strip_gps: true,
             strip_camera: true,
             strip_software: true,
@@ -395,16 +444,6 @@ fn build_ui(app: &adw::Application) {
         });
     }
 
-    // Wire help button to show contextual help for current step
-    {
-        let wizard = ui.state.wizard.clone();
-        let window_ref = window.clone();
-        help_button.connect_clicked(move |_| {
-            let step = wizard.borrow().current_step;
-            show_step_help(&window_ref, step);
-        });
-    }
-
     setup_window_actions(&window, &ui);
     update_nav_buttons(
         &ui.state.wizard.borrow(),