chore: sync Gitea 28.3.0 inputs and compatibility docs

CONTRIBUTING.md

@@ -69,10 +69,10 @@ The root lock file records the Gitea tag, its commit and file SHA-256 hashes. `v
 
 #### Updating the Official Version
 
-Use `sync` only when reviewing a new official version. For example, to explicitly synchronize to `v28.2.0`:
+Use `sync` only when reviewing a new official version. For example, to explicitly synchronize to `v28.3.0`:
 
 ```bash
-go run . upstream sync --tag v28.2.0
+go run . upstream sync --tag v28.3.0
 go run . upstream verify
 go test ./...
 go run . preview all
@@ -347,7 +347,7 @@ Use concise commit messages. The following prefixes are available as a reference
 Release tags must match the locked Gitea tag. Version labels, badges and compatibility records are maintained manually; changing official inputs does not trigger automatic version maintenance. Retain historical release assets and check documentation and compatibility records before tagging. After validation and generation of all previews, you can package manually from the repository root:
 
 ```bash
-python .github/scripts/package_release.py --version v28.2.0 --output build/release-review
+python .github/scripts/package_release.py --version v28.3.0 --output build/release-review
 ```
 
 Replace the example version with the tag in the root lock file and use an output directory without release archives of the same name. The script checks source and artifact hashes, packages themes, previews, documentation, the official license and provenance, and excludes stale theme builds.