feat(fase-13): admin UI + sidebar entry + isServerAdmin store + e2e SA-01..04

13.3 admin UI:
  - (admin) route group with own layout + red banner + sidebar (Collectives,
    Admins, Audit log, Server). +layout.ts is client-rendered (ssr=false),
    same rationale as the (app) group.
  - /admin/collectives — paginated list via admin_list_collectives, search
    by name, soft-delete / restore / hard-delete modals (hard-delete needs
    explicit checkbox; force toggle bypasses the 30-day wait server-side).
  - /admin/collectives/[id] — members list with kick action; recent actions
    for the collective filtered from admin_actions.
  - /admin/admins — list via server_admins join to users (disambiguated by
    FK name — there are TWO FKs to users so the embed needs the explicit
    server_admins_user_id_fkey); promote modal does an email lookup; revoke
    button is replaced by "you (cannot revoke yourself while sole admin)"
    when applicable.
  - /admin/audit — paginated feed (default 50), action filter.
  - /admin/server — server-layer default-section toggles backed by
    admin_set_default_section + the new admin_clear_default_section RPC
    (added because patching the JSONB to `true` is NOT equivalent to "no
    opinion" — `true` explicitly overrides a collective OFF).

13.4 sidebar/drawer entry:
  - $isServerAdmin store (writable; +$isServerAdminLoaded for the gate
    race) refreshed on every onAuthStateChange in root layout, cleared on
    sign-out. Cached so the sidebar tile is synchronous.
  - DesktopSidebar + MobileDrawer render the entry only when the store is
    true. Distinct red icon so it never blends with normal nav.

Stores wiring:
  - features.ts gains serverSectionDefaults writable + enabledSections
    derived now reads server > collective > user > default. Loader
    piggybacks on loadCurrentUserFeatures so the server layer is fetched
    once per sign-in.
  - serverAdmin.ts new module — refreshServerAdminFlag() + clearServerAdminFlag().
  - Tracks isServerAdminLoaded so the (admin) layout doesn't redirect away
    during the millisecond between SIGNED_IN and the RPC resolving (caught
    empirically — every hard-load to /admin/* bounced to / without it).

13.5 tests:
  - admin.test.ts (SA-01..SA-04) with new loginAsAdmin fixture. Ana is the
    seed admin (server_admins seeded via supabase/seed.sql).
  - SA-04 + SV-02 reset their server-layer JSONB via the new
    admin_clear_default_section RPC so the suites don't leak state into
    each other.

Migration 025 adds admin_clear_default_section(text) — same SECURITY DEFINER
+ audit pattern as the rest. pgTAP 017 updated (23 plans, AR-T13b + the
SECURITY DEFINER list now includes the clear RPC).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/src/lib/components/layout/DesktopSidebar.svelte

@@ -3,11 +3,12 @@
 	import { displayName } from '$lib/stores/auth';
 	import { currentCollective, userCollectives } from '$lib/stores/collective';
 	import { enabledSections } from '$lib/stores/features';
+	import { isServerAdmin } from '$lib/stores/serverAdmin';
 	import type { SectionKey } from '@colectivo/types';
 	import Avatar from '$lib/components/Avatar.svelte';
 	import CreateCollectiveModal from '$lib/components/CreateCollectiveModal.svelte';
 	import * as m from '$lib/paraglide/messages';
-	import { ShoppingCart, CheckSquare, FileText, Search, Settings, Plus } from 'lucide-svelte';
+	import { ShoppingCart, CheckSquare, FileText, Search, Settings, Plus, Shield } from 'lucide-svelte';
 
 	// Fase 12.3.1: nav items declared with their section key so we can filter
 	// by $enabledSections (precedence resolved client-side; see features.ts).
@@ -100,6 +101,18 @@
 	</nav>
 
 	<div class="p-3 pt-2">
+		{#if $isServerAdmin}
+			<!-- Fase 13.4: server-admin entry. Distinct red icon so it doesn't
+			     blend with normal app nav. Hidden for non-admins. -->
+			<a
+				href="/admin"
+				data-testid="sidebar-admin-link"
+				class="mb-2 flex items-center gap-2 rounded-md border border-red-200 bg-red-50/50 px-3 py-2 text-sm font-medium text-red-700 hover:bg-red-50 dark:border-red-900/60 dark:bg-red-950/20 dark:text-red-300 dark:hover:bg-red-950/40"
+			>
+				<Shield size={14} strokeWidth={1.5} />
+				{m.admin_menu_entry()}
+			</a>
+		{/if}
 		<div class="flex items-center justify-between gap-2">
 			<div class="flex min-w-0 items-center gap-2">
 				<Avatar name={$displayName} size={32} />

apps/web/src/lib/components/layout/MobileDrawer.svelte

@@ -1,11 +1,12 @@
 <script lang="ts">
 	import { currentCollective, userCollectives } from '$lib/stores/collective';
 	import { displayName } from '$lib/stores/auth';
+	import { isServerAdmin } from '$lib/stores/serverAdmin';
 	import Avatar from '$lib/components/Avatar.svelte';
 	import CreateCollectiveModal from '$lib/components/CreateCollectiveModal.svelte';
 	import { logout } from '$lib/auth';
 	import * as m from '$lib/paraglide/messages';
-	import { Settings, Users, LogOut, X, Plus } from 'lucide-svelte';
+	import { Settings, Users, LogOut, X, Plus, Shield } from 'lucide-svelte';
 
 	let showCreate = $state(false);
 
@@ -98,6 +99,18 @@
 				<Avatar name={$displayName} size={28} />
 				<span class="truncate text-sm font-medium text-text-primary">{$displayName}</span>
 			</div>
+			{#if $isServerAdmin}
+				<!-- Fase 13.4: server-admin entry. Same gating as DesktopSidebar. -->
+				<a
+					href="/admin"
+					onclick={close}
+					data-testid="drawer-admin-link"
+					class="flex items-center gap-2 rounded-md px-2 py-2 text-sm font-medium text-red-700 hover:bg-red-50 dark:text-red-300 dark:hover:bg-red-950/40"
+				>
+					<Shield size={14} strokeWidth={1.5} />
+					{m.admin_menu_entry()}
+				</a>
+			{/if}
 			<a
 				href="/settings"
 				onclick={close}