feat(glass): градиентный бордер — сверху белый засвет -> снизу прозрачно

- токен --v12-glass-neutral-border-grad (dark/light)
- mask-псевдоэлемент ::before рисует 1px градиентный бордер с сохранением border-radius
- нативный border-color -> transparent у glass-блоков, шапки, nav-more, floating

public/css/main.css

@@ -560,7 +560,7 @@ a:visited:not(.btn):not(.fab):not(.logo):not(.skip-link):hover {
   margin-top: 0;
   margin-bottom: 0;
   padding: 0.8rem;
-  border: 1px solid var(--line);
+  border: 1px solid transparent;
   border-radius: calc(var(--radius-card) * 0.7);
   background: var(--bg-elevated);
   box-shadow: 0 16px 38px hsla(0, 0%, 0%, 0.2);
@@ -755,6 +755,7 @@ a:visited:not(.btn):not(.fab):not(.logo):not(.skip-link):hover {
   right: 0;
   z-index: 90;
   background: var(--bg-elevated);
+  border-color: transparent;
 }
 
 /* Плавающая панель: fixed + координаты из JS; фон — токены v12-glass внизу файла */
@@ -5134,6 +5135,13 @@ html[data-theme="dark"] {
     color-mix(in srgb, var(--surface) 52%, transparent)
   );
   --v12-glass-neutral-border: color-mix(in srgb, var(--line) 75%, hsla(0, 0%, 100%, 0.08));
+  /* Градиентный бордер: сверху белый засвет -> снизу прозрачно */
+  --v12-glass-neutral-border-grad: linear-gradient(
+    to bottom,
+    hsla(0, 0%, 100%, 0.55) 0%,
+    hsla(0, 0%, 100%, 0.16) 38%,
+    hsla(0, 0%, 100%, 0) 100%
+  );
   --v12-glass-neutral-shadow:
     0 14px 32px hsla(0, 0%, 0%, 0.4),
     inset 0 1px 0 hsla(0, 0%, 100%, 0.09);
@@ -5151,6 +5159,13 @@ html[data-theme="light"] {
     color-mix(in srgb, var(--bg-elevated) 38%, transparent)
   );
   --v12-glass-neutral-border: color-mix(in srgb, var(--line) 58%, hsla(0, 0%, 0%, 0.07));
+  /* Градиентный бордер: сверху белый засвет -> снизу прозрачно (light: ярче) */
+  --v12-glass-neutral-border-grad: linear-gradient(
+    to bottom,
+    hsla(0, 0%, 100%, 0.9) 0%,
+    hsla(0, 0%, 100%, 0.3) 42%,
+    hsla(0, 0%, 100%, 0) 100%
+  );
   --v12-glass-neutral-shadow:
     0 14px 28px hsla(var(--theme-h), 22%, 38%, 0.11),
     inset 0 1px 0 hsla(0, 0%, 100%, 0.9),
@@ -5165,7 +5180,7 @@ html[data-theme="light"] {
 html[data-theme="dark"] .header--scrolled .header__inner,
 html[data-theme="light"] .header--scrolled .header__inner {
   background: var(--v12-glass-neutral-bg);
-  border-color: var(--v12-glass-neutral-border);
+  border-color: transparent;
   box-shadow: var(--v12-glass-neutral-shadow);
   backdrop-filter: var(--v12-glass-neutral-filter-elevated);
   -webkit-backdrop-filter: var(--v12-glass-neutral-filter-elevated);
@@ -5176,12 +5191,50 @@ html[data-theme="light"] .header--scrolled .header__inner {
 html[data-theme="dark"] .glass-neutral,
 html[data-theme="light"] .glass-neutral {
   background: var(--v12-glass-neutral-bg);
-  border-color: var(--v12-glass-neutral-border);
+  border-color: transparent;
   box-shadow: var(--v12-glass-neutral-shadow);
   backdrop-filter: var(--v12-glass-neutral-filter);
   -webkit-backdrop-filter: var(--v12-glass-neutral-filter);
 }
 
+/* Градиентный бордер (сверху засвет -> снизу прозрачно) через mask.
+   Исключаем .fab (там ::before занят shine). */
+html[data-theme="dark"] .glass-neutral:not(.fab),
+html[data-theme="light"] .glass-neutral:not(.fab),
+html[data-theme="dark"] .header--scrolled .header__inner,
+html[data-theme="light"] .header--scrolled .header__inner,
+html[data-theme="dark"] .nav-more__dock,
+html[data-theme="light"] .nav-more__dock,
+html[data-theme="dark"] #nav-more-menu-floating,
+html[data-theme="light"] #nav-more-menu-floating {
+  position: relative;
+}
+html[data-theme="dark"] .glass-neutral:not(.fab)::before,
+html[data-theme="light"] .glass-neutral:not(.fab)::before,
+html[data-theme="dark"] .header--scrolled .header__inner::before,
+html[data-theme="light"] .header--scrolled .header__inner::before,
+html[data-theme="dark"] .nav-more__dock::before,
+html[data-theme="light"] .nav-more__dock::before,
+html[data-theme="dark"] #nav-more-menu-floating::before,
+html[data-theme="light"] #nav-more-menu-floating::before {
+  content: "";
+  position: absolute;
+  inset: 0;
+  border-radius: inherit;
+  padding: 1px;
+  background: var(--v12-glass-neutral-border-grad);
+  -webkit-mask:
+    linear-gradient(#000 0 0) content-box,
+    linear-gradient(#000 0 0);
+  -webkit-mask-composite: xor;
+  mask:
+    linear-gradient(#000 0 0) content-box,
+    linear-gradient(#000 0 0);
+  mask-composite: exclude;
+  pointer-events: none;
+  z-index: 1;
+}
+
 html[data-theme="dark"] .theme-picker__panel.glass-neutral,
 html[data-theme="dark"] .cookie-notice.glass-neutral,
 html[data-theme="light"] .theme-picker__panel.glass-neutral,
@@ -5282,7 +5335,7 @@ html[data-theme="light"] .nav-more__dock,
 html[data-theme="dark"] #nav-more-menu-floating,
 html[data-theme="light"] #nav-more-menu-floating {
   background: var(--v12-glass-neutral-bg);
-  border-color: var(--v12-glass-neutral-border);
+  border-color: transparent;
   box-shadow: var(--v12-glass-neutral-shadow);
   backdrop-filter: var(--v12-glass-neutral-filter-elevated);
   -webkit-backdrop-filter: var(--v12-glass-neutral-filter-elevated);