refactor!: disk-first zero-copy architecture with file-to-file cwebp conversion

BREAKING CHANGE: Complete refactoring of the conversion pipeline.

- Replace in-memory Page/PageContainer with disk-based PageFile struct
- Extract archives to temp directory instead of loading into memory
- Use cwebp InputFile/OutputFile for zero-copy file-to-file conversion
- Use cwebp -crop for splitting (no Go-side image decode needed)
- Check if already converted before extracting (fast pre-check)
- Remove oliamb/cutter dependency (replaced by cwebp -crop)
- Remove page_container.go (no longer needed)
- Add comprehensive tests with improved coverage

Co-authored-by: Belphemur <197810+Belphemur@users.noreply.github.com>

go.mod

@@ -7,14 +7,12 @@ require (
 	github.com/belphemur/go-webpbin/v2 v2.1.0
 	github.com/fsnotify/fsnotify v1.10.1
 	github.com/mholt/archives v0.1.5
-	github.com/oliamb/cutter v0.2.2
 	github.com/rs/zerolog v1.35.1
 	github.com/samber/lo v1.53.0
 	github.com/spf13/cobra v1.10.2
 	github.com/spf13/viper v1.21.0
 	github.com/stretchr/testify v1.11.1
 	github.com/thediveo/enumflag/v2 v2.2.1
-	golang.org/x/exp v0.0.0-20260611194520-c48552f49976
 	golang.org/x/image v0.43.0
 )
 
@@ -50,7 +48,9 @@ require (
 	github.com/ulikunitz/xz v0.5.15 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	go4.org v0.0.0-20230225012048-214862532bf5 // indirect
-	golang.org/x/sys v0.45.0 // indirect
+	golang.org/x/net v0.56.0 // indirect
+	golang.org/x/sys v0.46.0 // indirect
 	golang.org/x/text v0.38.0 // indirect
+	golang.org/x/tools v0.46.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )