fix(ui): fix library selection state for single-library users (#4686)

* fix: validate library selection state for single-library users

Fixes issues where users with a single library see no content when
selectedLibraries in localStorage contains library IDs they no longer
have access to (e.g., after removing libraries or switching accounts).

Changes:
- libraryReducer: Validate selectedLibraries when SET_USER_LIBRARIES
  is dispatched, filtering out invalid IDs and resetting to empty for
  single-library users (empty means 'all accessible libraries')
- wrapperDataProvider: Add defensive validation in getSelectedLibraries
  to check against current user libraries before applying filters
- Add comprehensive test coverage for reducer validation logic

Fixes #4553, #4508, #4569

* style: format code with prettier

ui/src/dataProvider/wrapperDataProvider.js

@@ -12,7 +12,21 @@ const isAdmin = () => {
 const getSelectedLibraries = () => {
   try {
     const state = JSON.parse(localStorage.getItem('state'))
-    return state?.library?.selectedLibraries || []
+    const selectedLibraries = state?.library?.selectedLibraries || []
+    const userLibraries = state?.library?.userLibraries || []
+
+    // Validate selected libraries against current user libraries
+    const userLibraryIds = userLibraries.map((lib) => lib.id)
+    const validatedSelection = selectedLibraries.filter((id) =>
+      userLibraryIds.includes(id),
+    )
+
+    // If user has only one library, return empty array (no filter needed)
+    if (userLibraryIds.length === 1) {
+      return []
+    }
+
+    return validatedSelection
   } catch (err) {
     return []
   }