fix(packages): Add label for private and internal package and fix composor package source permission check (#37610) (#37643)

Backport #37610 by @lunny

- Add permission checks for Composer package source links

- Add private/internal visibility labels for packages, similar to
repository visibility labels

<img width="969" height="571" alt="image"
src="https://github.com/user-attachments/assets/8a8ec3a0-bfbd-4dd6-b45b-58eda5db1a2d"
/>

- Add a link to change package visibility

<img width="1309" height="208" alt="image"
src="https://github.com/user-attachments/assets/3fa82b23-4c63-4a5e-b3f0-d37a103231ee"
/>

- Update link package descriptions

<img width="1308" height="265" alt="image"
src="https://github.com/user-attachments/assets/2c80b50e-5ffe-4d96-aedd-aa15964c4e05"
/>

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: silverwind <me@silverwind.io>

routers/api/packages/composer/composer.go

@@ -146,6 +146,7 @@ func PackageMetadata(ctx *context.Context) {
 	}
 
 	resp := createPackageMetadataResponse(
+		ctx,
 		setting.AppURL+"api/packages/"+ctx.Package.Owner.Name+"/composer",
 		pds,
 	)