feat(design): Fjord, a trial fifth scheme — Midnight's navy with a steel-blue accent and steel rules (E28)

frontend/src/index.css

@@ -356,6 +356,14 @@ html[data-backdrop="on"][data-theme="dark"][data-scheme="matrix"] body {
     ),
     url("/backdrops/matrix.svg");
 }
+html[data-backdrop="on"][data-theme="dark"][data-scheme="fjord"] body {
+  background-image:
+    linear-gradient(
+      color-mix(in srgb, var(--bg) var(--bg-fade), transparent),
+      color-mix(in srgb, var(--bg) var(--bg-fade), transparent)
+    ),
+    url("/backdrops/fjord.svg");
+}
 html[data-backdrop="on"][data-theme="light"][data-scheme="midnight"] body {
   background-image:
     linear-gradient(
@@ -388,6 +396,14 @@ html[data-backdrop="on"][data-theme="light"][data-scheme="matrix"] body {
     ),
     url("/backdrops/light/matrix.svg");
 }
+html[data-backdrop="on"][data-theme="light"][data-scheme="fjord"] body {
+  background-image:
+    linear-gradient(
+      color-mix(in srgb, var(--bg) var(--bg-fade), transparent),
+      color-mix(in srgb, var(--bg) var(--bg-fade), transparent)
+    ),
+    url("/backdrops/light/fjord.svg");
+}
 html[data-backdrop="on"][data-theme="dark"] body,
 html[data-backdrop="on"][data-theme="light"] body {
   background-size: cover;
@@ -984,6 +1000,32 @@ html[data-scheme="matrix"][data-theme="light"] {
   --accent-fg: #ffffff;
 }
 
+/* Fjord — TRIAL, not yet a member of the set (docs/DESIGN.md decision log, B2 exception, 2026-09-25):
+   Midnight's navy with Playnite's calm — a muted steel-blue accent and steel rules instead of the vivid
+   periwinkle. It shares Midnight's hue family on purpose; the owner tries it app-wide, then it is folded
+   into Midnight or removed (normalizeTheme lands a stored "fjord" on the default either way). Playnite's
+   own accent (#337599) is 3.7:1 as text, so the accent is the same hue lifted to 6.5:1. */
+html[data-scheme="fjord"][data-theme="dark"] {
+  --bg: #0d1225;
+  --surface: #121931;
+  --card: #161e38;
+  --border: #25506e;
+  --fg: #eef1f5;
+  --muted: #9fb0c4;
+  --accent: #5aa1cb;
+  --accent-fg: #0d1225;
+}
+html[data-scheme="fjord"][data-theme="light"] {
+  --bg: #f3f6fa;
+  --surface: #ffffff;
+  --card: #ffffff;
+  --border: #c9d6e3;
+  --fg: #152232;
+  --muted: #4f6278;
+  --accent: #256b8f;
+  --accent-fg: #ffffff;
+}
+
 /* ===== Semantic status colors (danger / warn / success) =====
    Scheme-INDEPENDENT, theme-scoped: a status color is recognised by its conventional
    hue (red=danger), so it stays constant across schemes and only shifts by theme to