Wire resize algorithm selection, overwrite behavior, and fix rotation/flip scope

- Add ResizeAlgorithm enum (Lanczos3/CatmullRom/Bilinear/Nearest) to core
- Thread algorithm selection from UI ComboRow through ProcessingJob to resize_image
- Add OverwriteBehavior enum (AutoRename/Overwrite/Skip) to core
- Implement overwrite handling in executor with auto-rename suffix logic
- Wire overwrite behavior from output step through to processing job
- Fix rotation/flip to apply when resize step is enabled, not just adjustments

pixstrip-gtk/src/app.rs

@@ -18,6 +18,7 @@ pub struct JobConfig {
     pub resize_width: u32,
     pub resize_height: u32,
     pub allow_upscale: bool,
+    pub resize_algorithm: u32,
     // Adjustments
     pub adjustments_enabled: bool,
     pub rotation: u32,
@@ -222,6 +223,7 @@ fn build_ui(app: &adw::Application) {
             resize_width: if remember { sess_state.resize_width.unwrap_or(1200) } else { 1200 },
             resize_height: if remember { sess_state.resize_height.unwrap_or(0) } else { 0 },
             allow_upscale: false,
+            resize_algorithm: 0,
             adjustments_enabled: false,
             rotation: 0,
             flip: 0,
@@ -1255,6 +1257,12 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
                 allow_upscale: cfg.allow_upscale,
             });
         }
+        job.resize_algorithm = match cfg.resize_algorithm {
+            1 => pixstrip_core::operations::ResizeAlgorithm::CatmullRom,
+            2 => pixstrip_core::operations::ResizeAlgorithm::Bilinear,
+            3 => pixstrip_core::operations::ResizeAlgorithm::Nearest,
+            _ => pixstrip_core::operations::ResizeAlgorithm::Lanczos3,
+        };
     }
 
     if cfg.convert_enabled {
@@ -1344,8 +1352,8 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
         });
     }
 
-    // Rotation, Flip, and Adjustments (only when adjustments step is enabled)
-    if cfg.adjustments_enabled {
+    // Rotation and Flip apply from the resize step, so enable when either resize or adjustments is active
+    if cfg.resize_enabled || cfg.adjustments_enabled {
         job.rotation = Some(match cfg.rotation {
             1 => pixstrip_core::operations::Rotation::Cw90,
             2 => pixstrip_core::operations::Rotation::Cw180,
@@ -1359,7 +1367,10 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
             2 => pixstrip_core::operations::Flip::Vertical,
             _ => pixstrip_core::operations::Flip::None,
         });
+    }
 
+    // Adjustments (brightness, contrast, etc.)
+    if cfg.adjustments_enabled {
         let crop = match cfg.crop_aspect_ratio {
             1 => Some((1.0, 1.0)),
             2 => Some((4.0, 3.0)),
@@ -1436,6 +1447,12 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
     }
 
     job.preserve_directory_structure = cfg.preserve_dir_structure;
+    job.overwrite_behavior = match cfg.overwrite_behavior {
+        1 => pixstrip_core::operations::OverwriteBehavior::AutoRename,
+        2 => pixstrip_core::operations::OverwriteBehavior::Overwrite,
+        3 => pixstrip_core::operations::OverwriteBehavior::Skip,
+        _ => pixstrip_core::operations::OverwriteBehavior::AutoRename, // 0 "Ask" defaults to auto-rename in batch
+    };
 
     drop(cfg);