patches: add v1.6.0 de-brand series and register it as latest

Rebase the webui de-brand patch onto upstream versitygw v1.6.0 (clean
git am --3way, no conflicts). The de-branded HTML files are unchanged
between v1.5.0 and v1.6.0, so the series is byte-identical apart from
blob hashes; verified the result on a fresh v1.6.0 checkout (titles,
wordmark, removed logos/favicon all correct).

- patches/v1.6.0/0001-webui-debrand.patch (--binary export)
- ci/support-matrix.yaml: v1.6.0 added as the top/latest entry
- README.md: layout tree + maintained-versions table updated

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -38,6 +38,8 @@ s3-gateway/
 │   ├── publish-release.sh    # upload dist/* to a Gitea release
 │   └── run.sh                # local end-to-end: clone + patch + build one tag
 ├── patches/
+│   ├── v1.6.0/
+│   │   └── 0001-webui-debrand.patch
 │   └── v1.5.0/
 │       └── 0001-webui-debrand.patch
 ├── .gitea/workflows/build.yml
@@ -77,6 +79,7 @@ Currently maintained:
 
 | Upstream tag | Patch set     | Contents                          |
 |--------------|---------------|-----------------------------------|
+| `v1.6.0`     | `v1.6.0/`     | `0001-webui-debrand.patch`        |
 | `v1.5.0`     | `v1.5.0/`     | `0001-webui-debrand.patch`        |
 
 ### What the de-brand patch does

ci/support-matrix.yaml

@@ -12,5 +12,7 @@
 #   patches  directory under patches/ to apply (defaults to `tag`)
 
 versitygw:
+  - tag: v1.6.0
+    patches: v1.6.0
   - tag: v1.5.0
     patches: v1.5.0