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/utils/templateEngine.ts

@@ -6,6 +6,31 @@ export function hasTemplates(url: string): boolean {
   return TEMPLATE_RE.test(url);
 }
 
+/**
+ * Old bot backends resolve prefix-hardcoded Subpage templates
+ * (happ://crypt4/{{HAPP_CRYPT4_LINK}}) into happ://crypt4/happ://cryptN/... —
+ * strip the outer prefix so the deep link stays openable.
+ */
+export function collapseDoubledCryptPrefix(url: string): string {
+  return url.replace(/^happ:\/\/crypt\d+\/(?=happ:\/\/crypt)/i, '');
+}
+
+// jsencrypt's RSA-4096 takes up to tens of ms on weak devices and its padding is
+// random (a new string every call) — cache per subscription URL so render-time
+// resolution is cheap and stable within a session. Any single ciphertext is valid.
+const cryptLinkCache = new Map<string, string | null>();
+
+function cachedHappCryptoLink(url: string, version: 'v3' | 'v4'): string | null {
+  const key = `${version}|${url}`;
+  let link = cryptLinkCache.get(key);
+  if (link === undefined) {
+    if (cryptLinkCache.size >= 100) cryptLinkCache.clear();
+    link = createHappCryptoLink(url, version, true);
+    cryptLinkCache.set(key, link);
+  }
+  return link;
+}
+
 interface ResolveContext {
   subscriptionUrl: string;
   username?: string;
@@ -14,6 +39,11 @@ interface ResolveContext {
 export function resolveTemplate(template: string, ctx: ResolveContext): string {
   let result = template;
 
+  // {{HAPP_CRYPT*_LINK}} resolves to a FULL happ://crypt.../ deep link; when the
+  // template also hardcodes the prefix (happ://crypt4/{{HAPP_CRYPT4_LINK}}),
+  // collapse it so we don't produce happ://crypt4/happ://crypt5/...
+  result = result.replace(/happ:\/\/crypt\d+\/(?=\{\{HAPP_CRYPT[34]_LINK\}\})/gi, '');
+
   result = result.replace(/\{\{SUBSCRIPTION_LINK\}\}/g, ctx.subscriptionUrl);
 
   if (ctx.username) {
@@ -21,11 +51,11 @@ export function resolveTemplate(template: string, ctx: ResolveContext): string {
   }
 
   result = result.replace(/\{\{HAPP_CRYPT3_LINK\}\}/g, () => {
-    return createHappCryptoLink(ctx.subscriptionUrl, 'v3', true) ?? ctx.subscriptionUrl;
+    return cachedHappCryptoLink(ctx.subscriptionUrl, 'v3') ?? ctx.subscriptionUrl;
   });
 
   result = result.replace(/\{\{HAPP_CRYPT4_LINK\}\}/g, () => {
-    return createHappCryptoLink(ctx.subscriptionUrl, 'v4', true) ?? ctx.subscriptionUrl;
+    return cachedHappCryptoLink(ctx.subscriptionUrl, 'v4') ?? ctx.subscriptionUrl;
   });
 
   return result;