feat(cabinet): migrate all icons to the panel's Phosphor set

Replace the cabinet's hand-written heroicons-style SVG icon components with
the Remnawave panel's own icon family — Phosphor via react-icons/pi (Duotone).
All icons now live in a single central barrel (src/components/icons:
index + extended-icons + editor-icons, 144 icons); every feature file imports
from it instead of redefining inline SVGs (~440 icon defs removed).

- Add react-icons dependency
- Desktop nav (AppShell) now uses the central Phosphor icons, removing a
  stroke-vs-duotone inconsistency the partial migration introduced
- Icons with custom props (SortIcon's direction, expandable chevrons) kept as
  thin Phosphor wrappers; the RemnawaveIcon brand logo and animated SVGs
  (checkmarks, spinners) are intentionally left as-is
- Restore the original per-call-site icon sizes wherever the centralized
  default differed (211 call sites)

src/pages/AdminPromoOffers.tsx

@@ -5,59 +5,7 @@ import { useQuery } from '@tanstack/react-query';
 import i18n from '../i18n';
 import { promoOffersApi, PromoOfferLog, OFFER_TYPE_CONFIG, OfferType } from '../api/promoOffers';
 import { usePlatform } from '../platform/hooks/usePlatform';
-
-// Icons
-const BackIcon = () => (
-  <svg
-    className="h-5 w-5 text-dark-400"
-    fill="none"
-    viewBox="0 0 24 24"
-    stroke="currentColor"
-    strokeWidth={2}
-  >
-    <path strokeLinecap="round" strokeLinejoin="round" d="M15.75 19.5L8.25 12l7.5-7.5" />
-  </svg>
-);
-
-const EditIcon = () => (
-  <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
-    <path
-      strokeLinecap="round"
-      strokeLinejoin="round"
-      d="M16.862 4.487l1.687-1.688a1.875 1.875 0 112.652 2.652L10.582 16.07a4.5 4.5 0 01-1.897 1.13L6 18l.8-2.685a4.5 4.5 0 011.13-1.897l8.932-8.931zm0 0L19.5 7.125M18 14v4.75A2.25 2.25 0 0115.75 21H5.25A2.25 2.25 0 013 18.75V8.25A2.25 2.25 0 015.25 6H10"
-    />
-  </svg>
-);
-
-const SendIcon = () => (
-  <svg className="h-5 w-5" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
-    <path
-      strokeLinecap="round"
-      strokeLinejoin="round"
-      d="M6 12L3.269 3.126A59.768 59.768 0 0121.485 12 59.77 59.77 0 013.27 20.876L5.999 12zm0 0h7.5"
-    />
-  </svg>
-);
-
-const ClockIcon = () => (
-  <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
-    <path
-      strokeLinecap="round"
-      strokeLinejoin="round"
-      d="M12 6v6h4.5m4.5 0a9 9 0 11-18 0 9 9 0 0118 0z"
-    />
-  </svg>
-);
-
-const UserIcon = () => (
-  <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
-    <path
-      strokeLinecap="round"
-      strokeLinejoin="round"
-      d="M15.75 6a3.75 3.75 0 11-7.5 0 3.75 3.75 0 017.5 0zM4.501 20.118a7.5 7.5 0 0114.998 0A17.933 17.933 0 0112 21.75c-2.676 0-5.216-.584-7.499-1.632z"
-    />
-  </svg>
-);
+import { BackIcon, EditIcon, SendIcon, ClockIcon, UserIcon } from '@/components/icons';
 
 // Helper functions
 const formatDateTime = (date: string | null): string => {
@@ -295,7 +243,7 @@ export default function AdminPromoOffers() {
                   <div className="flex flex-col gap-3 sm:flex-row sm:items-start sm:justify-between sm:gap-4">
                     <div className="flex items-center gap-3">
                       <div className="flex h-10 w-10 shrink-0 items-center justify-center rounded-full bg-dark-700">
-                        <UserIcon />
+                        <UserIcon className="h-4 w-4" />
                       </div>
                       <div className="min-w-0">
                         <div className="mb-1 flex flex-wrap items-center gap-2">
@@ -317,7 +265,7 @@ export default function AdminPromoOffers() {
                       </div>
                     </div>
                     <div className="pl-13 flex items-center gap-1 text-xs text-dark-500 sm:pl-0">
-                      <ClockIcon />
+                      <ClockIcon className="h-4 w-4" />
                       {formatDateTime(log.created_at)}
                     </div>
                   </div>