fix(connection): keep the Happ add-subscription button working on Remnawave 2.8.0

Panel 2.8.0 removed the server-side happ-encrypt endpoint, so for users
without a stored crypto link the backend leaves {{HAPP_CRYPT4_LINK}}
unresolved and the subscriptionLink button silently disappeared
(isValidDeepLink requires '://').

- BlockButtons: resolve button templates client-side at render (with username,
  like the panel's own subpage) instead of dropping the button; collapse
  double-prefixed happ://crypt4/happ://cryptN/... resolvedUrl from old backends
- templateEngine: collapse a hardcoded happ://cryptN/ prefix before
  {{HAPP_CRYPT[34]_LINK}}; cache crypt-link generation (jsencrypt RSA-4096 is
  slow on weak devices and re-randomizes every call)
- Connection: in happ_cryptolink mode force the crypt link only when the button
  fell back to the plain subscription link or kept unresolved templates - an
  explicit Subpage link (e.g. happ://add/...) now wins, so Subpage edits apply

src/components/connection/InstallationGuide.tsx

@@ -48,6 +48,7 @@ interface Props {
   isTelegramWebApp: boolean;
   onGoBack: () => void;
   onOpenQR?: () => void;
+  username?: string;
 }
 
 export default function InstallationGuide({
@@ -56,6 +57,7 @@ export default function InstallationGuide({
   isTelegramWebApp,
   onGoBack,
   onOpenQR,
+  username,
 }: Props) {
   const { t, i18n } = useTranslation();
   const { isLight } = useTheme();
@@ -131,6 +133,7 @@ export default function InstallationGuide({
         subscriptionUrl={appConfig.subscriptionUrl}
         hideLink={appConfig.hideLink}
         deepLink={selectedApp?.deepLink}
+        username={username}
         getLocalizedText={getLocalizedText}
         getBaseTranslation={getBaseTranslation}
         getSvgHtml={getSvgHtml}
@@ -141,6 +144,7 @@ export default function InstallationGuide({
       appConfig.subscriptionUrl,
       appConfig.hideLink,
       selectedApp?.deepLink,
+      username,
       isLight,
       getLocalizedText,
       getBaseTranslation,

src/components/connection/blocks/BlockButtons.tsx

@@ -3,6 +3,7 @@ import { useTranslation } from 'react-i18next';
 import { CheckIcon, CopyIcon } from '@/components/icons';
 import type { RemnawaveButtonClient, LocalizedText } from '@/types';
 import { copyToClipboard } from '@/utils/clipboard';
+import { collapseDoubledCryptPrefix, hasTemplates, resolveTemplate } from '@/utils/templateEngine';
 import { blockButtonClass } from './buttonStyles';
 
 // eslint-disable-next-line no-script-url
@@ -29,6 +30,7 @@ interface BlockButtonsProps {
   subscriptionUrl: string | null;
   hideLink?: boolean;
   deepLink?: string | null;
+  username?: string;
   getLocalizedText: (text: LocalizedText | undefined) => string;
   getBaseTranslation: (key: string, i18nKey: string) => string;
   getSvgHtml: (key: string | undefined) => string;
@@ -42,6 +44,7 @@ export function BlockButtons({
   subscriptionUrl,
   hideLink,
   deepLink,
+  username,
   getLocalizedText,
   getBaseTranslation,
   getSvgHtml,
@@ -73,8 +76,17 @@ export function BlockButtons({
         ) : null;
 
         if (btn.type === 'subscriptionLink') {
-          const url = btn.resolvedUrl || btn.url || btn.link || deepLink || subscriptionUrl;
-          if (!url || !isValidDeepLink(url)) return null;
+          const raw = btn.resolvedUrl || btn.url || btn.link || deepLink || subscriptionUrl;
+          // The backend resolves {{HAPP_CRYPT*_LINK}} only when a crypto link is
+          // stored in the DB; since Remnawave 2.8.0 removed the encrypt endpoint,
+          // new users can get the raw template here. Resolve it client-side (the
+          // panel's own subpage does the same) instead of dropping the button.
+          const resolved =
+            raw && subscriptionUrl && hasTemplates(raw)
+              ? resolveTemplate(raw, { subscriptionUrl, username })
+              : raw;
+          const url = resolved ? collapseDoubledCryptPrefix(resolved) : resolved;
+          if (!url || hasTemplates(url) || !isValidDeepLink(url)) return null;
           return (
             <button
               key={idx}