refactor: remove unnecessary bg-color attributes and move to ui lib vars (#18234)

web/src/routes/admin/library-management/+page.svelte

@@ -298,9 +298,7 @@
           <tbody class="block overflow-y-auto rounded-md border dark:border-immich-dark-gray">
             {#each libraries as library, index (library.id)}
               <tr
-                class={`grid grid-cols-6 h-[80px] w-full place-items-center text-center dark:text-immich-dark-fg ${
-                  index % 2 == 0 ? 'bg-subtle' : 'bg-immich-bg dark:bg-immich-dark-gray/50'
-                }`}
+                class="grid grid-cols-6 h-[80px] w-full place-items-center text-center dark:text-immich-dark-fg even:bg-subtle/20 odd:bg-subtle/80"
               >
                 <td class="text-ellipsis px-4 text-sm">{library.name}</td>
                 <td class="text-ellipsis px-4 text-sm">

web/src/routes/admin/users/+page.svelte

@@ -103,13 +103,11 @@
         </thead>
         <tbody class="block w-full overflow-y-auto rounded-md border dark:border-immich-dark-gray">
           {#if allUsers}
-            {#each allUsers as immichUser, index (immichUser.id)}
+            {#each allUsers as immichUser (immichUser.id)}
               <tr
                 class="flex h-[80px] overflow-hidden w-full place-items-center text-center dark:text-immich-dark-fg {immichUser.deletedAt
                   ? 'bg-red-300 dark:bg-red-900'
-                  : index % 2 == 0
-                    ? 'bg-subtle'
-                    : 'bg-immich-bg dark:bg-immich-dark-gray/50'}"
+                  : 'even:bg-subtle/20 odd:bg-subtle/80'}"
               >
                 <td class="w-8/12 sm:w-5/12 lg:w-6/12 xl:w-4/12 2xl:w-5/12 text-ellipsis break-all px-2 text-sm"
                   ><Link href="{AppRoute.ADMIN_USERS}/{immichUser.id}">{immichUser.email}</Link></td