Use 比特骆驼 logo for PWA/brand marks, remove install button, docs Ubuntu 22.04 only.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/styles/app.css

@@ -81,70 +81,35 @@ input {
 }
 
 .brand {
+  display: inline-flex;
+  align-items: center;
+  gap: 8px;
   font-weight: 700;
   letter-spacing: 0.02em;
   color: var(--accent);
   white-space: nowrap;
   overflow: hidden;
   text-overflow: ellipsis;
+  min-width: 0;
 }
 
-.install-wrap {
-  position: relative;
+.brand-mark,
+.login-brand-mark {
   flex-shrink: 0;
+  border-radius: 6px;
+  object-fit: cover;
+  background: #1a1a1a;
 }
 
-.install-btn {
-  font-size: 12px;
-  padding: 4px 10px;
-  border: 1px solid var(--line);
-  color: var(--accent);
-}
-
-.install-badge {
-  display: inline-flex;
-  align-items: center;
-  font-size: 11px;
-  font-weight: 600;
-  letter-spacing: 0.04em;
-  padding: 3px 8px;
-  border-radius: 4px;
-  white-space: nowrap;
-}
-
-.install-badge.installed {
-  color: #0b0e11;
-  background: var(--accent);
-}
-
-.install-tip {
-  position: absolute;
-  top: calc(100% + 8px);
-  left: 0;
-  z-index: 30;
-  width: min(320px, calc(100vw - 24px));
-  padding: 12px;
-  border: 1px solid var(--line);
-  border-radius: 8px;
-  background: var(--bg-elev);
-  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.45);
-}
-
-.install-tip p {
-  margin: 0 0 8px;
-  font-size: 12px;
-  line-height: 1.5;
-  color: var(--text);
-}
-
-.install-tip p.muted,
-.install-tip .muted {
-  color: var(--muted);
+.login-brand-mark {
+  border-radius: 10px;
 }
 
 @media (max-width: 900px) {
-  .topnav-side.left .brand {
-    max-width: 11em;
+  .topnav-side.left .brand span {
+    max-width: 9em;
+    overflow: hidden;
+    text-overflow: ellipsis;
   }
 }
 
@@ -406,9 +371,8 @@ input {
 
 .login-title-row {
   display: flex;
-  align-items: flex-start;
-  justify-content: space-between;
-  gap: 10px;
+  align-items: center;
+  gap: 12px;
   margin-bottom: 20px;
 }