polish: Light theme redesign — soft off-white base, real text hierarchy

- Base shifts from #f5f5f5 to #fbfbfc (softer off-white, faint cool tint)
  — pure-white-card-on-soft-base elevation reads instead of being flat.
- bg-hover #f0f1f4 (darker on hover, the light-theme inverse).
- text-muted vs text-dim were near-identical (#697180 vs #6c717a) — no
  real hierarchy. Now #5b5f6e (WCAG AA on bg) and #888c98 for hints.
- Deeper violet accent #6d28d9 — carries more weight on white than the
  previous shade did.
- Semantic colours retuned for light backgrounds (zap, danger, warning,
  success all use the deeper Tailwind-700 family for proper presence).

src/lib/themes.ts

@@ -50,22 +50,22 @@ export const themes: Theme[] = [
     id: "light",
     name: "Light",
     colors: {
-      bg: "#f5f5f5",
+      bg: "#fbfbfc",
       "bg-raised": "#ffffff",
-      "bg-hover": "#e8e8e8",
-      border: "#d4d4d4",
-      "border-subtle": "#e5e5e5",
-      text: "#1a1a1a",
-      "text-muted": "#697180",
-      "text-dim": "#6c717a",
-      accent: "#7c3aed",
-      "accent-hover": "#6d28d9",
+      "bg-hover": "#f0f1f4",
+      border: "#e2e4e9",
+      "border-subtle": "#ecedf1",
+      text: "#1a1b22",
+      "text-muted": "#5b5f6e",
+      "text-dim": "#888c98",
+      accent: "#6d28d9",
+      "accent-hover": "#5b21b6",
       "accent-text": "#ffffff",
-      zap: "#d97706",
+      zap: "#c2410c",
       "zap-text": "#ffffff",
-      danger: "#dc2626",
-      warning: "#d97706",
-      success: "#16a34a",
+      danger: "#b91c1c",
+      warning: "#b45309",
+      success: "#15803d",
     },
   },
   {