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/AdminPromoOfferSend.tsx

@@ -12,59 +12,14 @@ import {
 } from '../api/promoOffers';
 import { adminUsersApi, UserListItem } from '../api/adminUsers';
 import { AdminBackButton } from '../components/admin';
-
-// Icons
-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 CheckIcon = () => (
-  <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
-    <path strokeLinecap="round" strokeLinejoin="round" d="M4.5 12.75l6 6 9-13.5" />
-  </svg>
-);
-
-const UsersIcon = () => (
-  <svg className="h-5 w-5" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={1.5}>
-    <path
-      strokeLinecap="round"
-      strokeLinejoin="round"
-      d="M15 19.128a9.38 9.38 0 002.625.372 9.337 9.337 0 004.121-.952 4.125 4.125 0 00-7.533-2.493M15 19.128v-.003c0-1.113-.285-2.16-.786-3.07M15 19.128v.106A12.318 12.318 0 018.624 21c-2.331 0-4.512-.645-6.374-1.766l-.001-.109a6.375 6.375 0 0111.964-3.07M12 6.375a3.375 3.375 0 11-6.75 0 3.375 3.375 0 016.75 0zm8.25 2.25a2.625 2.625 0 11-5.25 0 2.625 2.625 0 015.25 0z"
-    />
-  </svg>
-);
-
-const UserIcon = () => (
-  <svg className="h-5 w-5" 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>
-);
-
-const SearchIcon = () => (
-  <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
-    <path
-      strokeLinecap="round"
-      strokeLinejoin="round"
-      d="M21 21l-5.197-5.197m0 0A7.5 7.5 0 105.196 5.196a7.5 7.5 0 0010.607 10.607z"
-    />
-  </svg>
-);
-
-const CloseIcon = () => (
-  <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
-    <path strokeLinecap="round" strokeLinejoin="round" d="M6 18L18 6M6 6l12 12" />
-  </svg>
-);
+import {
+  SendIcon,
+  CheckIcon,
+  UsersIcon,
+  UserIcon,
+  SearchIcon,
+  CloseIcon,
+} from '@/components/icons';
 
 const getOfferTypeIcon = (offerType: string): string => {
   return OFFER_TYPE_CONFIG[offerType as OfferType]?.icon || '🎁';
@@ -420,7 +375,7 @@ export default function AdminPromoOfferSend() {
                       onClick={handleClearUser}
                       className="rounded-lg p-1.5 text-dark-400 transition-colors hover:bg-dark-600 hover:text-dark-100"
                     >
-                      <CloseIcon />
+                      <CloseIcon className="h-4 w-4" />
                     </button>
                   </div>
                 ) : (
@@ -428,7 +383,7 @@ export default function AdminPromoOfferSend() {
                   <>
                     <div className="relative">
                       <div className="pointer-events-none absolute left-3 top-1/2 -translate-y-1/2 text-dark-400">
-                        <SearchIcon />
+                        <SearchIcon className="h-4 w-4" />
                       </div>
                       <input
                         type="text"