Add a Central Tag-Management Screen#882

Please provide one place to manage tags across saved content. This request is about organizing and maintaining tags, not just adding tags to individual tabs.

• Show all tags in an alphabetized, searchable list.

• Allow users to rename, merge, and delete tags.

• Show how many saved links or collections use each tag.

• Preview which items will be affected before applying changes.

• When deleting a tag, clearly explain that the saved content will remain.

• Provide an Undo option for accidental changes.