refactor: consolidate icons and move server edit to separate page

- Create centralized icons file at src/components/icons/index.tsx
- Update admin and AppShell icons to re-export from centralized location
- Replace trial "T" button with GiftIcon in AdminServers
- Move server editing from modal to dedicated page /admin/servers/:id/edit
- Add localization keys for server edit page (mainSettings, pricingAndLimits, updateError)

src/locales/en.json

@@ -1382,7 +1382,10 @@
       "enable": "Enable",
       "disable": "Disable",
       "toggleTrial": "Toggle Trial",
-      "loadError": "Failed to load server"
+      "loadError": "Failed to load server",
+      "mainSettings": "Main Settings",
+      "pricingAndLimits": "Pricing & Limits",
+      "updateError": "Failed to save changes"
     },
     "campaigns": {
       "title": "Ad Campaigns",