Template inheritance is set once at create time and immutable on update.
UpdateTemplateAsync now returns "Parent template cannot be changed after
creation." when the caller sends a parent that differs from the stored
value — server-side enforcement covers UI, ManagementService, and CLI.
TemplateEdit renders the parent as static plaintext rather than an
editable dropdown; TemplateCreate's parent picker is unchanged.
Templates page is now a tree-only browser; editing happens on a dedicated
TemplateEdit page. Drag-drop is replaced by context-menu Move-to-Folder.
TreeView gains Bootstrap Icons (chevron + per-kind glyphs), ancestor guide
lines, defined hover/selected/focus tokens, and Escape-dismisses-menu per
the new Visual Design Guide (V1-V7) in Component-TreeView.md.
Joseph Doherty