feat(ui): warm light theme and pre-mixed status fills

- Light mode moves to Claude's ivory/terracotta family: page #e8e5da, cards
  #f5f3ec (a notch below Claude's ivory, no pure-white step), warm
  borders and card shadow; dark mode is untouched.
- The surface ramp rises in lightness with its index in BOTH themes, so a
  card sits brighter than the page and every hover lifts instead of dims.
- Light --accent #a34a28 (the brand #cc785c is 3.1:1 on ivory); --fg-muted
  held at >=4.5:1; new --syn-* syntax tokens, dark keeps its pastels.
- Status/accent fills (bg-*/N, border-*/N) compile to color-mix against
  --tint-base instead of rgb(/a), so a chip is one colour on every surface.
- Hardcoded dark-only hovers (hover:text-white, hover:bg-white/5) replaced
  by tokens in DateTimePicker and SessionDrillIn.

client/tailwind.config.js

@@ -8,6 +8,43 @@
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
+/**
+ * A status/accent FILL is pre-mixed against one fixed base, never translucent.
+ *
+ * `bg-status-success/10` used to emit `rgb(var(--status-success) / 0.1)`, which
+ * composites with whatever is behind it — so the one "success" chip rendered as
+ * five different colours over the five surface steps, and washed out badly on
+ * the light theme's near-white cards. Mixing against `--tint-base` (the card
+ * surface of the active theme) gives an OPAQUE colour: the same chip reads the
+ * same on the page, in a card, in a modal and inside an input row.
+ *
+ * Applied to `backgroundColor`/`borderColor` only. `text-status-warning/80` and
+ * `ring-accent/40` stay genuinely translucent — text and rings sit on top of a
+ * fill rather than replacing it — and the surface family keeps its alpha too,
+ * or every modal scrim would turn solid.
+ */
+const tint =
+  (variable) =>
+  ({ opacityValue }) => {
+    const alpha = Number(opacityValue);
+    // No modifier at all: Tailwind passes `var(--tw-bg-opacity, 1)` here.
+    if (!Number.isFinite(alpha) || alpha >= 1) return `rgb(var(${variable}))`;
+    return `color-mix(in srgb, rgb(var(${variable})) ${alpha * 100}%, rgb(var(--tint-base)))`;
+  };
+
+const tinted = {
+  accent: {
+    DEFAULT: tint("--accent"),
+    hover: tint("--accent-hover"),
+    muted: "color-mix(in srgb, rgb(var(--accent)) 15%, rgb(var(--tint-base)))",
+  },
+  status: {
+    success: tint("--status-success"),
+    danger: tint("--status-danger"),
+    warning: tint("--status-warning"),
+  },
+};
+
 /** @type {import('tailwindcss').Config} */
 export default {
   darkMode: "class",
@@ -37,12 +74,29 @@ export default {
           secondary: "rgb(var(--fg-secondary) / <alpha-value>)",
           muted: "rgb(var(--fg-muted) / <alpha-value>)",
         },
+        syntax: {
+          comment: "rgb(var(--syn-comment) / <alpha-value>)",
+          string: "rgb(var(--syn-string) / <alpha-value>)",
+          number: "rgb(var(--syn-number) / <alpha-value>)",
+          keyword: "rgb(var(--syn-keyword) / <alpha-value>)",
+          builtin: "rgb(var(--syn-builtin) / <alpha-value>)",
+          function: "rgb(var(--syn-function) / <alpha-value>)",
+          operator: "rgb(var(--syn-operator) / <alpha-value>)",
+          punctuation: "rgb(var(--syn-punctuation) / <alpha-value>)",
+          property: "rgb(var(--syn-property) / <alpha-value>)",
+          tag: "rgb(var(--syn-tag) / <alpha-value>)",
+          plain: "rgb(var(--syn-plain) / <alpha-value>)",
+          add: "rgb(var(--syn-add) / <alpha-value>)",
+          del: "rgb(var(--syn-del) / <alpha-value>)",
+        },
         status: {
           success: "rgb(var(--status-success) / <alpha-value>)",
           danger: "rgb(var(--status-danger) / <alpha-value>)",
           warning: "rgb(var(--status-warning) / <alpha-value>)",
         },
       },
+      backgroundColor: tinted,
+      borderColor: tinted,
       fontFamily: {
         sans: ["Inter", "-apple-system", "BlinkMacSystemFont", "Segoe UI", "sans-serif"],
         mono: ["JetBrains Mono", "Fira Code", "Consolas", "monospace"],