Add all wizard step UIs: workflow, images, resize, convert, compress, metadata, output

Full Adwaita widget-based layouts for all 7 wizard steps with
PreferencesGroups, SwitchRows, SpinRows, ComboRows, FlowBoxes,
ExpanderRows for social media presets, quality slider with named
marks, metadata radio group, and output configuration.

pixstrip-gtk/src/steps/step_compress.rs

@@ -0,0 +1,125 @@
+use adw::prelude::*;
+
+pub fn build_compress_page() -> adw::NavigationPage {
+    let scrolled = gtk::ScrolledWindow::builder()
+        .hscrollbar_policy(gtk::PolicyType::Never)
+        .vexpand(true)
+        .build();
+
+    let content = gtk::Box::builder()
+        .orientation(gtk::Orientation::Vertical)
+        .spacing(12)
+        .margin_top(12)
+        .margin_bottom(12)
+        .margin_start(24)
+        .margin_end(24)
+        .build();
+
+    // Enable toggle
+    let enable_row = adw::SwitchRow::builder()
+        .title("Enable Compression")
+        .subtitle("Reduce file size with quality control")
+        .active(true)
+        .build();
+
+    let enable_group = adw::PreferencesGroup::new();
+    enable_group.add(&enable_row);
+    content.append(&enable_group);
+
+    // Quality slider
+    let quality_group = adw::PreferencesGroup::builder()
+        .title("Quality Level")
+        .description("Higher quality means larger files")
+        .build();
+
+    let quality_scale = gtk::Scale::builder()
+        .orientation(gtk::Orientation::Horizontal)
+        .adjustment(&gtk::Adjustment::new(3.0, 1.0, 5.0, 1.0, 1.0, 0.0))
+        .draw_value(false)
+        .hexpand(true)
+        .build();
+    quality_scale.set_round_digits(0);
+
+    // Add named marks
+    quality_scale.add_mark(1.0, gtk::PositionType::Bottom, Some("Web"));
+    quality_scale.add_mark(2.0, gtk::PositionType::Bottom, Some("Low"));
+    quality_scale.add_mark(3.0, gtk::PositionType::Bottom, Some("Medium"));
+    quality_scale.add_mark(4.0, gtk::PositionType::Bottom, Some("High"));
+    quality_scale.add_mark(5.0, gtk::PositionType::Bottom, Some("Maximum"));
+
+    let quality_label = gtk::Label::builder()
+        .label("Medium - Good balance of quality and size")
+        .css_classes(["dim-label"])
+        .margin_top(4)
+        .build();
+
+    let quality_box = gtk::Box::builder()
+        .orientation(gtk::Orientation::Vertical)
+        .spacing(4)
+        .margin_top(8)
+        .margin_bottom(8)
+        .margin_start(12)
+        .margin_end(12)
+        .build();
+    quality_box.append(&quality_scale);
+    quality_box.append(&quality_label);
+
+    quality_group.add(&quality_box);
+    content.append(&quality_group);
+
+    // Size estimation placeholder
+    let estimate_group = adw::PreferencesGroup::builder()
+        .title("Size Estimation")
+        .description("Load images to see real compression results")
+        .build();
+
+    let estimate_row = adw::ActionRow::builder()
+        .title("Estimated savings")
+        .subtitle("Add images to see file size comparison")
+        .build();
+    estimate_row.add_prefix(&gtk::Image::from_icon_name("drive-harddisk-symbolic"));
+
+    estimate_group.add(&estimate_row);
+    content.append(&estimate_group);
+
+    // Advanced options
+    let advanced_group = adw::PreferencesGroup::builder()
+        .title("Advanced Options")
+        .build();
+
+    let jpeg_row = adw::SpinRow::builder()
+        .title("JPEG Quality")
+        .subtitle("1-100, higher is better quality")
+        .adjustment(&gtk::Adjustment::new(85.0, 1.0, 100.0, 1.0, 10.0, 0.0))
+        .build();
+
+    let png_row = adw::SpinRow::builder()
+        .title("PNG Compression Level")
+        .subtitle("1-6, higher is slower but smaller")
+        .adjustment(&gtk::Adjustment::new(3.0, 1.0, 6.0, 1.0, 1.0, 0.0))
+        .build();
+
+    let webp_row = adw::SpinRow::builder()
+        .title("WebP Quality")
+        .subtitle("1-100, higher is better quality")
+        .adjustment(&gtk::Adjustment::new(80.0, 1.0, 100.0, 1.0, 10.0, 0.0))
+        .build();
+
+    advanced_group.add(&jpeg_row);
+    advanced_group.add(&png_row);
+    advanced_group.add(&webp_row);
+    content.append(&advanced_group);
+
+    scrolled.set_child(Some(&content));
+
+    let clamp = adw::Clamp::builder()
+        .maximum_size(600)
+        .child(&scrolled)
+        .build();
+
+    adw::NavigationPage::builder()
+        .title("Compress")
+        .tag("step-compress")
+        .child(&clamp)
+        .build()
+}