refactor(admin): phase 7 — delete old tab components and page.server.ts

Remove UsersTab, GroupsTab, TagsTab, SystemTab and their specs; delete
the monolithic +page.server.ts with shared load + 6 form actions (all
now handled by dedicated sub-route servers under users/, groups/, tags/).
Add delete action and confirmation button to user edit panel.
Fix test to query the edit form by id rather than the first form in DOM.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/admin/users/[id]/+page.server.ts

@@ -1,4 +1,4 @@
-import { error, fail } from '@sveltejs/kit';
+import { error, fail, redirect } from '@sveltejs/kit';
 import type { PageServerLoad, Actions } from './$types';
 import { createApiClient } from '$lib/api.server';
 import { getErrorMessage } from '$lib/errors';
@@ -63,5 +63,19 @@ export const actions: Actions = {
 		}
 
 		return { success: true };
+	},
+
+	delete: async ({ params, fetch }) => {
+		const api = createApiClient(fetch);
+		const result = await api.DELETE('/api/users/{id}', {
+			params: { path: { id: params.id } }
+		});
+
+		if (!result.response.ok) {
+			const code = (result.error as unknown as { code?: string })?.code;
+			return fail(result.response.status, { error: getErrorMessage(code) });
+		}
+
+		throw redirect(303, '/admin/users');
 	}
 };

frontend/src/routes/admin/users/[id]/+page.svelte

@@ -16,6 +16,25 @@ const selectedGroupIds = $derived(data.editUser.groups?.map((g: { id: string })
 		<h2 class="flex-1 font-sans text-sm font-bold text-ink">
 			{m.admin_user_edit_heading({ username: data.editUser.username })}
 		</h2>
+		<form
+			method="POST"
+			action="?/delete"
+			use:enhance={({ cancel }) => {
+				if (!confirm(m.admin_user_delete_confirm({ username: data.editUser.username }))) {
+					cancel();
+				}
+				return async ({ update }) => {
+					await update();
+				};
+			}}
+		>
+			<button
+				type="submit"
+				class="rounded-sm border border-red-200 bg-red-50 px-3 py-1 font-sans text-xs font-bold tracking-widest text-red-700 uppercase transition-colors hover:bg-red-100 dark:border-red-900 dark:bg-red-950/30 dark:text-red-400"
+			>
+				{m.btn_delete()}…
+			</button>
+		</form>
 	</div>
 
 	<!-- Scrollable body -->

frontend/src/routes/admin/users/[id]/page.svelte.spec.ts

@@ -96,7 +96,7 @@ describe('Admin edit user page – rendering', () => {
 
 	it('includes pre-selected group ids in FormData at submit time (guards against groupIds being empty)', async () => {
 		render(Page, { data: baseData, form: null });
-		const form = document.querySelector('form')!;
+		const form = document.querySelector<HTMLFormElement>('form#edit-user-form')!;
 		const formData = new FormData(form);
 		expect(formData.getAll('groupIds')).toContain('g1');
 		expect(formData.getAll('groupIds')).not.toContain('g2');