site cleanup: remove dead listings, fix HTML issues, add SEO tags

- Remove Cake Wallet (delisted WOW) and YellWOWPages (dead)
- Remove legacy index_russian.html (ru.json translation exists)
- Add OpenGraph + Twitter Card meta tags for link previews
- Add meta description and theme-color
- Add sitemap.xml
- Fix CSS typo: !importa -> !important in footer
- Fix duplicate HTML IDs (exvolunt, wowb, exc, walletss)
- Fix malformed IDs (-mroadmap -> m-roadmap, m-whitepapers -> m-whitepaper)
- Fix nested <p> tags in explain sections
- Fix mobile funding URL to match desktop (funding.wownero.com)
- Remove empty <h3 id=""> element
- Add LANG dropdown and bottom nav to mining.html
- Update pt-BR/pt-PT translations for new IDs
- Promote Stack Wallet as primary wallet

mining.html

@@ -20,7 +20,7 @@
     <link href="css/aos.css" rel="stylesheet">
     <script src="js/translations/traduction.js"></script>
 </head>
-<body onload="translate(navigator.language)" style="overflow-x: hidden;">
+<body onload="translate(localStorage.getItem('wowLang') || navigator.language)" style="overflow-x: hidden;">
 
 <script>
     AOS.init({
@@ -33,7 +33,7 @@
             <img src="img/Wownero_Brand_Mono.svg" alt="Wownero Brand" width="220px">
         </a>
         <a class="navbar-brand-two text-center d-lg-none d-inline-block" href="index.html">
-            <img src="img/Wownero_Brand_Mono.svg" alt="Wownero Logo" class="navbar-toggler" height="48" data-toggle="collapse" data-target="#myNavbar">
+            <img src="img/Wownero_Brand_Mono.svg" alt="Wownero Logo" height="48">
         </a>
     </div>
             <div class="d-none d-lg-block">
@@ -47,27 +47,41 @@
             </li>
             <li class="nav-item">
                 <a href="index.html#wallets" class="myButton" id="walletss">WALLETS</a>
-            </li> 
-        </ul>
-    </div>
-</div>
-    <div class="d-lg-none">
-    <div class="collapse navbar-collapse flex-grow-1 text-right" id="myNavbar">
-        <ul class="navbar-nav ml-auto flex-nowrap">
-            <li class="nav-item">
-                <a href="https://suchwow.xyz/" class="myButton-mobile-nav" id="m-navmeme">MEMES</a>
             </li>
-            <li class="nav-item">
-                <a href="https://codeberg.org/wownero/" class="myButton-mobile-nav" id="m-navcode">CODE</a>
-            </li>
-            <li class="nav-item">
-                <a href="index.html#wallets" class="myButton-mobile-nav" id="walletss">WALLETS</a>
+            <li class="nav-item dropdown">
+                <a class="myButton dropdown-toggle" href="#" id="langDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">LANG</a>
+                <div class="dropdown-menu dropdown-menu-right" aria-labelledby="langDropdown">
+                    <a class="dropdown-item" href="#" onclick="translate('en-US'); return false;">English</a>
+                    <a class="dropdown-item" href="#" onclick="translate('fr-FR'); return false;">Fran&#231;ais</a>
+                    <a class="dropdown-item" href="#" onclick="translate('it-IT'); return false;">Italiano</a>
+                    <a class="dropdown-item" href="#" onclick="translate('ru'); return false;">&#1056;&#1091;&#1089;&#1089;&#1082;&#1080;&#1081;</a>
+                    <a class="dropdown-item" href="#" onclick="translate('pt-BR'); return false;">Portugu&#234;s (BR)</a>
+                    <a class="dropdown-item" href="#" onclick="translate('pt-PT'); return false;">Portugu&#234;s (PT)</a>
+                </div>
             </li>
         </ul>
     </div>
 </div>
 </nav>
 
+<!-- Mobile bottom nav bar -->
+<nav class="mobile-bottom-nav">
+    <a href="index.html" class="mobile-bottom-nav-item">HOME</a>
+    <a href="https://suchwow.xyz/" class="mobile-bottom-nav-item" id="m-navmeme">MEMES</a>
+    <a href="https://codeberg.org/wownero/" class="mobile-bottom-nav-item" id="m-navcode">CODE</a>
+    <div class="mobile-bottom-nav-item dropup">
+        <a href="#" class="mobile-bottom-nav-link" id="langDropdownMobile" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">LANG</a>
+        <div class="dropdown-menu" aria-labelledby="langDropdownMobile">
+            <a class="dropdown-item" href="#" onclick="translate('en-US'); return false;">English</a>
+            <a class="dropdown-item" href="#" onclick="translate('fr-FR'); return false;">Fran&#231;ais</a>
+            <a class="dropdown-item" href="#" onclick="translate('it-IT'); return false;">Italiano</a>
+            <a class="dropdown-item" href="#" onclick="translate('ru'); return false;">&#1056;&#1091;&#1089;&#1089;&#1082;&#1080;&#1081;</a>
+            <a class="dropdown-item" href="#" onclick="translate('pt-BR'); return false;">Portugu&#234;s (BR)</a>
+            <a class="dropdown-item" href="#" onclick="translate('pt-PT'); return false;">Portugu&#234;s (PT)</a>
+        </div>
+    </div>
+</nav>
+
 <div class="container-fluid">
     <div class="row" data-aos="fade-right">
         <div class="col-md-12">