chore: drop redundant background repaints so surfaces inherit their parent (#27576)

* chore: drop redundant background repaints so surfaces inherit their parent

Four spots repaint the exact color their parent surface already provides
(bg-white / dark:bg-gray-900 rows inside same-colored pages and modals,
and the selectClass dark repaint inside the connection modals — the
sibling input const is already fully transparent). Visually identical in
stock light and dark; removing them lets instance theming show through
instead of leaving opaque boxes:

- .tiptap tr (app.css) — table rows in notes/editors
- Edit User Group Users tab body rows (common Modal surface)
- AddToolServerModal + AddTerminalServerModal selectClass dark repaint

The matching repaints inside the ModelUsage/UserUsage components are
not part of this change — those files were dead code and were removed
entirely in #27574.

* chore: catch remaining redundant surface repaints missed in the first pass

Same rule as the previous commit — every one of these repaints the exact
color its parent surface already provides, so removal is stock-identical
in light and dark while letting instance theming show through:

- Analytics Dashboard's inline Model Usage / User Activity row markup
  (the Analytics tab renders these tables from Dashboard.svelte itself;
  the unreferenced ModelUsage/UserUsage component files were removed
  in #27574)
- Evaluations Feedbacks + Leaderboard body rows (settings modal surface)
- admin UserList body rows (app page surface)
- chat markdown tables (MarkdownTokens): thead and body rows — unlike
  the tiptap header (gray-850 contrast, untouched), this thead painted
  the page's own color
- CitationsModal source rows (common Modal surface)
- AddConnectionModal selectClass dark repaint — third copy of the same
  const already fixed in AddToolServerModal / AddTerminalServerModal

src/lib/components/admin/Analytics/Dashboard.svelte

@@ -468,7 +468,7 @@
 					<tbody>
 						{#each sortedModels as model, idx (model.model_id)}
 							<tr
-								class="bg-white dark:bg-gray-900 dark:border-gray-850 text-xs cursor-pointer hover:bg-gray-50 dark:hover:bg-gray-800 transition-colors"
+								class="dark:border-gray-850 text-xs cursor-pointer hover:bg-gray-50 dark:hover:bg-gray-800 transition-colors"
 								on:click={() => {
 									selectedModel = { id: model.model_id, name: model.name };
 									showModelModal = true;
@@ -581,7 +581,7 @@
 					</thead>
 					<tbody>
 						{#each sortedUsers as user, idx (user.user_id)}
-							<tr class="bg-white dark:bg-gray-900 dark:border-gray-850 text-xs">
+							<tr class="dark:border-gray-850 text-xs">
 								<td class="px-3 py-1 text-gray-400">{idx + 1}</td>
 								<td class="px-3 py-1 font-normal text-gray-900 dark:text-white">
 									<div class="flex items-center gap-2">

src/lib/components/admin/Evaluations/Feedbacks.svelte

@@ -418,7 +418,7 @@
 					<tbody class="">
 						{#each items as feedback (feedback.id)}
 							<tr
-								class="bg-white dark:bg-gray-900 dark:border-gray-850 text-xs cursor-pointer hover:bg-gray-50 dark:hover:bg-gray-850/50 transition rounded-xl"
+								class="dark:border-gray-850 text-xs cursor-pointer hover:bg-gray-50 dark:hover:bg-gray-850/50 transition rounded-xl"
 								on:click={() => openFeedbackModal(feedback)}
 							>
 								<td class=" py-0.5 text-right font-normal">

src/lib/components/admin/Evaluations/Leaderboard.svelte

@@ -201,7 +201,7 @@
 				<tbody>
 					{#each sortedModels as model, idx (model.id)}
 						<tr
-							class="bg-white dark:bg-gray-900 text-xs group cursor-pointer hover:bg-gray-50 dark:hover:bg-gray-850/50 transition"
+							class="text-xs group cursor-pointer hover:bg-gray-50 dark:hover:bg-gray-850/50 transition"
 							on:click={() => openModal(model)}
 						>
 							<td class="px-3 py-1.5 font-normal text-gray-900 dark:text-white">

src/lib/components/admin/Users/Groups/Users.svelte

@@ -234,7 +234,7 @@
 					</thead>
 					<tbody class="">
 						{#each users as user, userIdx (user?.id ?? userIdx)}
-							<tr class="bg-white dark:bg-gray-900 dark:border-gray-850 text-xs">
+							<tr class="dark:border-gray-850 text-xs">
 								<td class=" px-3 py-1 w-8">
 									<div class="flex w-full justify-center">
 										<Checkbox

src/lib/components/admin/Users/UserList.svelte

@@ -346,7 +346,7 @@
 			</thead>
 			<tbody class="">
 				{#each users as user (user.id)}
-					<tr class="bg-white dark:bg-gray-900 dark:border-gray-850 text-xs">
+					<tr class="dark:border-gray-850 text-xs">
 						<td class="px-3 py-1 font-normal text-gray-900 dark:text-white max-w-48">
 							<div class="flex items-center gap-2">
 								<ProfilePreview {user} side="right" align="center" sideOffset={6}>