feat: add object versioning support

Implements object versioning capabilities (v0.15.0) including:
- Bucket APIs: PutBucketVersioning, GetBucketVersioning
- Object Listing: ListVersions (lists versions and delete markers)
- Object Operations: Updated FileDownload, FileDelete, and FileDetails to support VersionId
- Integration tests covering the full versioning workflow (enable, upload versions, list, download specific version, delete specific version)

Documentation updated in README.md and ROADMAP.md.

"I have implemented Object Versioning (v0.15.0) as per the roadmap."

README.md

@@ -16,6 +16,7 @@ using AWS Signature Version 4.
 - **Simple List API** with pagination, prefix filtering, and delimiter grouping
 - **Iterator-based ListAll** for memory-efficient large bucket iteration (Go 1.23+)
 - **Presigned URL generation** for secure browser uploads/downloads (including multipart)
+- **Object Versioning** - Enable versioning, list versions, and access specific object versions
 - **IAM credential support** for EC2 instances
 - **Comprehensive test coverage**
 - **Zero dependencies** - uses only Go standard library
@@ -417,6 +418,73 @@ Note: Tag support during upload varies by operation:
 - **FileUpload** (POST): ⚠️  AWS S3 supported, MinIO limited (does not support tags in POST policy)
 - **CopyObject**: ✅ Full support (handles MinIO/R2 signature quirks automatically)
 
+### Object Versioning
+
+Enable and manage object versions to protect against accidental deletion or overwrite.
+
+#### Enable Versioning
+
+```go
+err := s3.PutBucketVersioning(simples3.PutBucketVersioningInput{
+    Bucket: "my-bucket",
+    Status: "Enabled", // or "Suspended"
+})
+if err != nil {
+    log.Fatal(err)
+}
+
+// Check status
+config, err := s3.GetBucketVersioning("my-bucket")
+fmt.Printf("Versioning status: %s\n", config.Status)
+```
+
+#### List Object Versions
+
+List all versions of objects in a bucket:
+
+```go
+result, err := s3.ListVersions(simples3.ListVersionsInput{
+    Bucket: "my-bucket",
+    Prefix: "important-file.txt",
+})
+if err != nil {
+    log.Fatal(err)
+}
+
+for _, version := range result.Versions {
+    fmt.Printf("Key: %s, VersionId: %s, IsLatest: %v\n",
+        version.Key, version.VersionId, version.IsLatest)
+}
+```
+
+#### Download Specific Version
+
+Retrieve a specific version of an object:
+
+```go
+file, err := s3.FileDownload(simples3.DownloadInput{
+    Bucket:    "my-bucket",
+    ObjectKey: "my-file.txt",
+    VersionId: "v1-version-id",
+})
+if err != nil {
+    log.Fatal(err)
+}
+// Use file (io.ReadCloser) normally
+```
+
+#### Delete Specific Version
+
+Delete a specific version of an object:
+
+```go
+err := s3.FileDelete(simples3.DeleteInput{
+    Bucket:    "my-bucket",
+    ObjectKey: "my-file.txt",
+    VersionId: "v1-version-id",
+})
+```
+
 ### Multipart Upload
 
 For large files (>100MB), use multipart upload for better performance, resumability, and parallel uploads.