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-core/src/operations/resize.rs

@@ -3,11 +3,19 @@ use fast_image_resize::{images::Image, Resizer, ResizeOptions, ResizeAlg, Filter
 use crate::error::{PixstripError, Result};
 use crate::types::Dimensions;
 
-use super::ResizeConfig;
+use super::{ResizeConfig, ResizeAlgorithm};
 
 pub fn resize_image(
     src: &image::DynamicImage,
     config: &ResizeConfig,
+) -> Result<image::DynamicImage> {
+    resize_image_with_algorithm(src, config, ResizeAlgorithm::default())
+}
+
+pub fn resize_image_with_algorithm(
+    src: &image::DynamicImage,
+    config: &ResizeConfig,
+    algorithm: ResizeAlgorithm,
 ) -> Result<image::DynamicImage> {
     let original = Dimensions {
         width: src.width(),
@@ -40,7 +48,13 @@ pub fn resize_image(
     );
 
     let mut resizer = Resizer::new();
-    let options = ResizeOptions::new().resize_alg(ResizeAlg::Convolution(FilterType::Lanczos3));
+    let alg = match algorithm {
+        ResizeAlgorithm::Lanczos3 => ResizeAlg::Convolution(FilterType::Lanczos3),
+        ResizeAlgorithm::CatmullRom => ResizeAlg::Convolution(FilterType::CatmullRom),
+        ResizeAlgorithm::Bilinear => ResizeAlg::Convolution(FilterType::Bilinear),
+        ResizeAlgorithm::Nearest => ResizeAlg::Nearest,
+    };
+    let options = ResizeOptions::new().resize_alg(alg);
 
     resizer
         .resize(&src_image, &mut dst_image, &options)