Tint the landing nav from the theme, not from a dark constant

The fixed bar sat on a hardcoded rgba(9, 10, 15, 0.72), so switching the
page to light left it dark under dark text. --lp-nav now carries the tint in
both palettes.

docker/frontend/src/styles/landing.css

@@ -16,6 +16,9 @@
   --lp-text: #f3f4f6;
   --lp-muted: #9ca3af;
   --lp-line: rgba(255, 255, 255, 0.08);
+  /* Translucent bar tint — must follow the theme, not just --lp-bg, because the
+     fixed nav keeps this tint while the page scrolls under it. */
+  --lp-nav: rgba(9, 10, 15, 0.72);
   /* Amber for text sitting on the page background — darker in light mode,
      where plain #fbbf24 would fail contrast on white. */
   --lp-ink-amber: var(--lp-amber);
@@ -38,6 +41,7 @@
   --lp-text: #14161c;
   --lp-muted: #5b6472;
   --lp-line: rgba(20, 22, 28, 0.12);
+  --lp-nav: rgba(247, 247, 248, 0.72);
   --lp-ink-amber: #a16207;
 }
 [data-theme="light"] .lp-hero h1 { background: linear-gradient(100deg, #14161c 8%, var(--lp-amber) 62%, var(--lp-red) 98%); -webkit-background-clip: text; background-clip: text; }
@@ -104,7 +108,7 @@ html { scroll-behavior: smooth; scroll-padding-top: 78px; }
   position: fixed;
   inset: 0 0 auto 0;
   z-index: 50;
-  background: rgba(9, 10, 15, 0.72);
+  background: var(--lp-nav);
   backdrop-filter: blur(14px);
   -webkit-backdrop-filter: blur(14px);
   border-bottom: 1px solid var(--lp-line);