- Fixed directory pattern matching: go-gitignore doesn't match 'build/'
  against bare 'build', now checks with trailing slash appended
- Added ModTime to FileMeta for reliable change detection (same-size
  file modifications now sync correctly)
- Updated Dockerfile to golang:1.24-alpine (was 1.22)
- Downgraded go.mod to Go 1.24 (system has custom 1.26.4 build)

Docker tested with podman:
- Initial sync correctly excludes ignored dirs/files
- Nested .gitignore works (sub/ ignores *.tmp)
- Watcher syncs new/modified/deleted files
- Case-sensitive rename (Foo→foo) handled correctly
- Same-size file modifications sync correctly

- main.go: CLI entry point with flag parsing
- gitignore.go: .gitignore loading and parsing
- sync.go: initial sync with manifest tracking
- watcher.go: fsnotify-based file watcher with debouncing
- Dockerfile: multi-stage build for Alpine runtime