Docker test fixes: directory pattern matching, mtime-based sync, Go version

- 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

1 files changed, 5 insertions, 3 deletions

diff --git a/watcher.go b/watcher.go
index 2067887..192b61b 100644
--- a/watcher.go
+++ b/watcher.go
@@ -127,6 +127,7 @@ func syncCreate(srcPath, destPath, relPath string, manifest *Manifest, stack *Gi
 	meta := FileMeta{
 		Size:    info.Size(),
 		Mode:    info.Mode(),
+		ModTime: info.ModTime(),
 		Symlink: linkTarget,
 	}
 	manifest.Files[relPath] = meta
@@ -161,13 +162,14 @@ func syncWrite(srcPath, destPath, relPath string, manifest *Manifest, dryRun, ve
 	}
 
 	meta, exists := manifest.Files[relPath]
-	if exists && meta.Size == info.Size() && meta.Mode == info.Mode() {
+	if exists && meta.Size == info.Size() && meta.Mode == info.Mode() && meta.ModTime.Equal(info.ModTime()) {
 		return
 	}
 
 	manifest.Files[relPath] = FileMeta{
-		Size: info.Size(),
-		Mode: info.Mode(),
+		Size:    info.Size(),
+		Mode:    info.Mode(),
+		ModTime: info.ModTime(),
 	}
 
 	if dryRun {