fix(frontend): session cookie path, browser-language default, avatar crop, EN link previews, topbar logo

- nginx: rewrite the refresh cookie's Path=/auth to /api/auth on the
  production proxy — without this the browser never sent the cookie
  back on POST /api/auth/refresh and the session was lost on reload
- i18n: fallbackLng ru -> en, so only an actual ru browser locale
  defaults to Russian, everything else defaults to English
- index.html: explicit English og:*/twitter:* tags so link previews
  in Discord/etc. don't fall back to the (Russian) meta description
- Avatar upload: pick -> circular crop/reposition/zoom preview ->
  confirm -> upload, instead of uploading the raw file blind
- Topbar: logo pill background removed, pixel-heart mark added next
  to the LoVisual wordmark
- Fixed two tests left stale by the earlier tagline copy change

Claude-Session: https://claude.ai/code/session_01F1M1Jic1wTSn4igUENynmZ

frontend/index.html

@@ -1,15 +1,34 @@
 <!doctype html>
-<html lang="ru">
+<html lang="en">
   <head>
     <meta charset="UTF-8" />
-    <link rel="icon" type="image/svg+xml" href="/favicon.svg" />
+    <link rel="icon" type="image/svg+xml" href="/favicon.svg?v=2" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <meta name="theme-color" content="#0d1416" />
     <meta
       name="description"
-      content="LoVisual, визуальный мод для Minecraft, в который влюбляешься. Крылья, 3D меню, погода с отражениями и облачные конфиги."
+      content="LoVisual, a Minecraft visuals mod you'll fall in love with. Wings, a floating 3D menu, rain with reflections and cloud configs."
     />
-    <title>LoVisual · визуалы, в которые влюбляешься</title>
+    <title>LoVisual, visuals you'll fall in love with</title>
+
+    <!-- Link previews (Discord, Slack, Telegram, X, ...) read these instead of <meta name=description>,
+         and render before the site's own JS-driven i18n can run, so they stay in English on purpose. -->
+    <meta property="og:type" content="website" />
+    <meta property="og:site_name" content="LoVisual" />
+    <meta property="og:title" content="LoVisual, visuals you'll fall in love with" />
+    <meta
+      property="og:description"
+      content="A free legit Minecraft visuals mod. Wings, a floating 3D menu, rain with reflections and cloud configs."
+    />
+    <meta property="og:url" content="https://visual.loki-code.dev/" />
+    <meta property="og:image" content="https://visual.loki-code.dev/favicon.png" />
+    <meta name="twitter:card" content="summary" />
+    <meta name="twitter:title" content="LoVisual, visuals you'll fall in love with" />
+    <meta
+      name="twitter:description"
+      content="A free legit Minecraft visuals mod. Wings, a floating 3D menu, rain with reflections and cloud configs."
+    />
+    <meta name="twitter:image" content="https://visual.loki-code.dev/favicon.png" />
   </head>
   <body>
     <div id="root"></div>