chore: add auto-generated ID backlog item

BACKLOG.md

@@ -17,6 +17,19 @@ Switching letters requires backspace to clear the accumulated string first.
 Fix requires replacing the native select with a custom dropdown component
 that handles keyboard search with a clean reset-on-idle timer.
 
+### Auto-generated IDs in admin forms (new units/groups)
+When the ID field is empty (or has only been auto-filled, not manually typed):
+- Auto-fill priority: kebab(symbol) first, then kebab(label) if symbol is empty or a duplicate
+- If symbol is typed first, symbol drives the ID. If label is typed first and symbol is empty,
+  label drives the ID. If symbol is later typed, it overrides the label-derived ID.
+- Auto-filled ID shown in a visually distinct style (e.g. washed-out color) to indicate
+  it has not been customized by the user.
+- If auto-filled ID is a duplicate, fall back to the other field. If both are duplicates,
+  block save and show an error until a unique ID is manually entered.
+- If the user types anything directly into the ID field, auto-generation is permanently
+  disabled for that edit session (manual input wins).
+- User cannot navigate away (except via Cancel/Escape) while ID is empty or duplicate.
+
 ---
 
 ## DONE