fix: hide chat delete actions when the chat delete permission is disabled (#27714)

The chat delete endpoints gate on chat.delete for non-admins, but none of
the UI affordances that reach them were conditioned on it, so a user
without the permission is offered controls that always fail with
"Access prohibited".

Gates every entry point on the same condition the backend enforces,
matching the existing chat.share / chat.export / chat.import gates in the
same components:

- Sidebar chat menu (ChatMenu) Delete item — also covers the Search
  modal's menu, which reuses ChatMenu
- Sidebar Shift+hover inline Delete button (ChatItem)
- Sidebar hidden #delete-chat-button keyboard-shortcut target (ChatItem)
- Chat navbar menu Delete item (Navbar/Menu)
- Search modal Shift-held inline Delete button (SearchModal)
- Settings -> Data Controls -> Delete All Chats
- Settings -> Archived Chats per-row Delete

src/lib/components/chat/Settings/ArchivedChats.svelte

@@ -19,7 +19,7 @@
 		getArchivedChatList,
 		unarchiveAllChats
 	} from '$lib/apis/chats';
-	import { chatId, showSettings } from '$lib/stores';
+	import { chatId, showSettings, user } from '$lib/stores';
 	import { refreshChatList } from '$lib/stores/chatList';
 	import { formatNumber } from '$lib/utils';
 	import ConfirmDialog from '$lib/components/common/ConfirmDialog.svelte';
@@ -348,19 +348,21 @@
 									<UndoAction className="size-3.5" strokeWidth="1.5" />
 								</button>
 							</Tooltip>
-							<Tooltip content={$i18n.t('Delete Chat')}>
-								<button
-									class="rounded-lg p-1 text-gray-400 transition-colors hover:text-gray-700 dark:text-gray-600 dark:hover:text-gray-300"
-									type="button"
-									aria-label={$i18n.t('Delete Chat')}
-									on:click={() => {
-										selectedChatId = chat.id;
-										showDeleteConfirmDialog = true;
-									}}
-								>
-									<Trash className="size-3.5" strokeWidth="1.5" />
-								</button>
-							</Tooltip>
+							{#if $user?.role === 'admin' || ($user?.permissions?.chat?.delete ?? true)}
+								<Tooltip content={$i18n.t('Delete Chat')}>
+									<button
+										class="rounded-lg p-1 text-gray-400 transition-colors hover:text-gray-700 dark:text-gray-600 dark:hover:text-gray-300"
+										type="button"
+										aria-label={$i18n.t('Delete Chat')}
+										on:click={() => {
+											selectedChatId = chat.id;
+											showDeleteConfirmDialog = true;
+										}}
+									>
+										<Trash className="size-3.5" strokeWidth="1.5" />
+									</button>
+								</Tooltip>
+							{/if}
 						</div>
 					</div>
 				{/each}

src/lib/components/chat/Settings/DataControls.svelte

@@ -216,20 +216,22 @@
 				</button>
 			</UserSettingRow>
 
-			<UserSettingRow
-				label={$i18n.t('Delete All Chats')}
-				description={$i18n.t('Permanently delete every chat after confirmation.')}
-			>
-				<button
-					class={actionButtonClass}
-					on:click={() => {
-						showDeleteConfirmDialog = true;
-					}}
-					type="button"
+			{#if $user?.role === 'admin' || ($user?.permissions?.chat?.delete ?? true)}
+				<UserSettingRow
+					label={$i18n.t('Delete All Chats')}
+					description={$i18n.t('Permanently delete every chat after confirmation.')}
 				>
-					{$i18n.t('Delete All')}
-				</button>
-			</UserSettingRow>
+					<button
+						class={actionButtonClass}
+						on:click={() => {
+							showDeleteConfirmDialog = true;
+						}}
+						type="button"
+					>
+						{$i18n.t('Delete All')}
+					</button>
+				</UserSettingRow>
+			{/if}
 		</UserSettingSection>
 
 		<UserSettingSection title={$i18n.t('Files')}>