fix: skip corrupt/unreadable images instead of aborting scan

- scan_images now warns and continues on decode errors
- new test: scan_skips_corrupt_image_files
- 21 tests passing

tests/image_phase.rs

@@ -109,6 +109,17 @@ fn single_image_no_duplicates() {
     assert!(groups.is_empty(), "single image should produce no duplicate groups");
 }
 
+#[test]
+fn scan_skips_corrupt_image_files() {
+    // corrupt.png exists in fixtures dir with invalid PNG data
+    let dir = Path::new("/a0/usr/projects/deduper/.a0proj/test_media/images");
+    let entries = scan_images(dir).expect("scan should not fail on corrupt files");
+    // corrupt.png should be skipped, not cause an error
+    assert!(!entries.iter().any(|e| e.path.ends_with("corrupt.png")), "corrupt file should be skipped");
+    // valid images still found
+    assert!(entries.iter().any(|e| e.path.ends_with("orig.jpg")), "valid images should still be found");
+}
+
 #[test]
 fn cli_binary_reports_duplicates() {
     let bin = env!("CARGO_BIN_EXE_deduper");