feat(appearance): Sahara theme

Built from the three sands an operator sent: #faf6eb for panels, #e8dfca
for the page behind them, #ddd2ba for toolbars, table headers and rows.
The ordering is what makes it work — a panel reads as lifted off the page
and the log grid as settled into it, so rows stay scannable without extra
rules. Ink is a deep warm brown; pure black on sand glares.

frontend/src/style.css

@@ -775,6 +775,79 @@
   color-scheme: light;
 }
 
+/* ---- Theme 1e: Sahara — warm sand, from an operator's own palette ---------
+   Three sands, lightest to darkest: panels sit on #faf6eb, the page behind them
+   on #e8dfca, and toolbars, table headers and rows on #ddd2ba. The order is the
+   point — a panel must read as lifted OFF the page, and the log grid as settled
+   INTO it, which is what makes rows scannable without lines everywhere.
+   Ink is a deep warm brown rather than black: pure black on sand glares. ---- */
+[data-theme="sahara"] {
+  --background: #e8dfca;            /* sand — the page */
+  --foreground: #2b2318;            /* deep warm brown-ink */
+  --card: #faf6eb;                  /* lifted panel / entry strip */
+  --card-foreground: #2b2318;
+  --popover: #faf6eb;
+  --popover-foreground: #2b2318;
+  --primary: #b45309;               /* burnt sienna */
+  --primary-foreground: #fffbf2;
+  --secondary: #ddd2ba;
+  --secondary-foreground: #2b2318;
+  --muted: #ddd2ba;                 /* toolbars / table headers — the darkest sand */
+  --muted-foreground: #5c503c;      /* readable on both sands */
+  --accent: #ecd9b8;                /* warm highlight */
+  --accent-foreground: #6b3a06;
+  --destructive: #b91c1c;
+  --destructive-foreground: #ffffff;
+  --destructive-muted: #fdecec;
+  --destructive-muted-foreground: #b91c1c;
+  --border: #c9bc9e;                /* sand a step down again, so edges read */
+  --input: #c9bc9e;
+  --ring: #d97706;                  /* amber focus ring */
+
+  --success: #15803d;
+  --success-foreground: #ffffff;
+  --success-muted: #dcf3e1;
+  --success-muted-foreground: #14532d;
+  --success-border: #86d99f;
+
+  --warning: #b45309;
+  --warning-foreground: #ffffff;
+  --warning-muted: #fbeacd;
+  --warning-muted-foreground: #7c3d05;
+  --warning-border: #e8b96a;
+
+  --caution: #a16207;
+  --caution-foreground: #1c1917;
+  --caution-muted: #f7edcb;
+  --caution-muted-foreground: #713f12;
+  --caution-border: #e0c069;
+
+  --danger: #be123c;
+  --danger-foreground: #ffffff;
+  --danger-muted: #fbe3e8;
+  --danger-muted-foreground: #9f1239;
+  --danger-border: #ee9aac;
+
+  --info: #0369a1;
+  --info-foreground: #ffffff;
+  --info-muted: #e0eef6;
+  --info-muted-foreground: #075985;
+  --info-border: #86c5e4;
+
+  /* Band/mode matrix — the app's blues kept, on a sand neutral so an empty slot
+     recedes into the grid instead of punching a hole in it. */
+  --mx-call-conf: #15803d;
+  --mx-call-work: #7fd6a4;
+  --mx-dx-conf:   #3730a3;
+  --mx-dx-work:   #a5b4fc;
+  --mx-none:      #ddd2ba;
+
+  --scrollbar-thumb: #c0b193;
+  --scrollbar-thumb-hover: #a89676;
+  --card-shadow: 0 1px 2px rgba(43, 35, 24, 0.07), 0 0 0 1px rgba(43, 35, 24, 0.03);
+  color-scheme: light;
+}
+
 /* ── Data-viz palette (Statistics dashboard) ────────────────────────────────
    A VALIDATED categorical palette, not hand-picked: the slot ORDER is what makes
    it colour-blind-safe (worst adjacent ΔE 24.2 light / 10.3 dark), so never
@@ -793,7 +866,8 @@
 [data-theme="light-warm"],
 [data-theme="light-cool"],
 [data-theme="light-sage"],
-[data-theme="light-nordic"] {
+[data-theme="light-nordic"],
+[data-theme="sahara"] {
   --chart-1: #2a78d6; /* blue    — default single-series hue */
   --chart-2: #1baf7a; /* aqua    */
   --chart-3: #eda100; /* yellow  */