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, 3 insertions, 0 deletions

diff --git a/sync.go b/sync.go
index 526e143..6bdd651 100644
--- a/sync.go
+++ b/sync.go
@@ -5,11 +5,13 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"time"
 )
 
 type FileMeta struct {
 	Size    int64
 	Mode    os.FileMode
+	ModTime time.Time
 	Symlink string
 }
 
@@ -65,6 +67,7 @@ func initialSync(hostDir, dataDir string, stack *GitignoreStack, dryRun bool) (*
 		meta := FileMeta{
 			Size:    info.Size(),
 			Mode:    info.Mode(),
+			ModTime: info.ModTime(),
 			Symlink: linkTarget,
 		}
 		manifest.Files[relPath] = meta