feat(config): RPC bootstrap hardening, socket alignment, and exhaustive tests (tinyhumansai#1313)

Author: M3gA-Mind

app/src/pages/Welcome.tsx

@@ -3,6 +3,7 @@ import { useState } from 'react';
 import OAuthProviderButton from '../components/oauth/OAuthProviderButton';
 import { oauthProviderConfigs } from '../components/oauth/providerConfigs';
 import RotatingTetrahedronCanvas from '../components/RotatingTetrahedronCanvas';
+import { clearBackendUrlCache } from '../services/backendUrl';
 import { clearCoreRpcUrlCache, testCoreRpcConnection } from '../services/coreRpcClient';
 import { useDeepLinkAuthState } from '../store/deepLinkAuthState';
 import {
@@ -39,6 +40,7 @@ const Welcome = () => {
 
     storeRpcUrl(normalized);
     clearCoreRpcUrlCache();
+    clearBackendUrlCache();
     setRpcUrlError(null);
     setSaveSuccess(true);
 
@@ -48,6 +50,7 @@ const Welcome = () => {
   const handleResetRpcUrl = () => {
     clearStoredRpcUrl();
     clearCoreRpcUrlCache();
+    clearBackendUrlCache();
     setRpcUrl(getDefaultRpcUrl());
     setRpcUrlError(null);
     setSaveSuccess(false);
@@ -71,6 +74,7 @@ const Welcome = () => {
         setSaveSuccess(true);
         storeRpcUrl(normalized);
         clearCoreRpcUrlCache();
+        clearBackendUrlCache();
       } else {
         setRpcUrlError(`Connection failed: ${response.status} ${response.statusText}`);
       }