fix(ui): derive Library Type dropdowns from library_types — audiobooks was missing

The audiobook library type shipped backend-complete (LibraryTypeAudiobooks
constant, allowed extensions, MIME map, schema seed row, GET
/api/libraries/types) but neither create-library form offered it: the
admin Create Library modal and the setup wizard's add-library step both
hardcoded their <option> lists to the original three types
(ebooks/comics/manga), so an audiobook library could not be created from
the UI.

Both dropdowns now render from the same DB-backed library_types table
the create API resolves types against — a future type appears without
template edits (the exact drift the rendering-ownership rule warns
about):

- templates/utils.go: OrderedLibraryTypes pins the historical dropdown
  order (ebooks, comics, manga, audiobooks) and appends unknown future
  types by name; LibraryTypeDisplayName renders labels with a
  capitalize-the-name fallback for types added without a label
- templates/admin_library.templ: new LibraryTypeOptions fragment used
  by the modal's select; AdminLibrary takes the types list
- templates/setup.templ: Setup takes the types list, same fragment
- internal/router/helpers.go: libraryTypeOptionsFor fetches via
  LibraryService.GetLibraryTypes, falling back to the built-in type
  names on DB failure so the forms stay usable (CreateLibrary still
  resolves the name against the DB, so the fallback is never
  authoritative)
- internal/router/frontend.go, internal/router/setup.go: pass the list
  into the two pages

Tests:
- templates/utils_test.go: pure unit tests for ordering + labels
- cmd/server/tests/admin_library_page_test.go: SSR regression —
  /admin/library must offer all four library types, audiobooks exactly
  once (options come from the DB loop, not a hardcode)

internal/router/frontend.go

@@ -1143,7 +1143,8 @@ func registerFrontendRoutes(cfg *Config) {
 
 		var buf bytes.Buffer
 		archivedCount, _ := cfg.Queries.CountArchivedMediaItems(c.Request().Context())
-		err = templates.AdminLibrary(user, libData, userData, archivedCount).Render(c.Request().Context(), &buf)
+		libraryTypes := libraryTypeOptionsFor(c.Request().Context(), cfg)
+		err = templates.AdminLibrary(user, libData, userData, archivedCount, libraryTypes).Render(c.Request().Context(), &buf)
 		if err != nil {
 			return err
 		}

internal/router/helpers.go

@@ -405,3 +405,24 @@ func (cfg *Config) loadCollectionBooksLite(c *echo.Context, userUUID uuid.UUID,
 	return cfg.collectionBooksForScope(c, userUUID, pgtype.UUID{Bytes: collUUID, Valid: true}, collection, collectionID,
 		libUUID, libUUID, libraryID != "", visibleIDs)
 }
+
+// libraryTypeOptionsFor loads the library_types rows for the create-library
+// dropdowns (admin page + setup wizard), ordered for display. On DB failure
+// it falls back to the built-in type names so the form stays usable —
+// CreateLibrary resolves the name against the DB, so this is never
+// authoritative.
+func libraryTypeOptionsFor(ctx context.Context, cfg *Config) []database.LibraryTypes {
+	types, err := cfg.LibraryService.GetLibraryTypes(ctx)
+	if err != nil {
+		log.Printf("libraryTypeOptionsFor: GetLibraryTypes failed, using built-in type names: %v", err)
+		for _, name := range []string{
+			services.LibraryTypeEbooks,
+			services.LibraryTypeComics,
+			services.LibraryTypeManga,
+			services.LibraryTypeAudiobooks,
+		} {
+			types = append(types, database.LibraryTypes{Name: name})
+		}
+	}
+	return templates.OrderedLibraryTypes(types)
+}

internal/router/setup.go

@@ -81,7 +81,8 @@ func registerSetupRoutes(cfg *Config) {
 			return c.Redirect(http.StatusFound, "/")
 		}
 		var buf bytes.Buffer
-		if err := templates.Setup().Render(c.Request().Context(), &buf); err != nil {
+		libraryTypes := libraryTypeOptionsFor(c.Request().Context(), cfg)
+		if err := templates.Setup(libraryTypes).Render(c.Request().Context(), &buf); err != nil {
 			log.Printf("Failed to render setup template: %v", err)
 			return c.HTML(http.StatusInternalServerError, "Failed to render setup page")
 		}