refactor(frontend): unify theme tokens to single --dg-* source

- remove shadcn HSL dual-track vars (523->416->~300 lines index.css);
  tailwind semantic colors (border/background/card/primary/destructive/
  popover/muted/accent) now bridge directly to var(--dg-*) tokens
- drop dead darkMode:['class'] config and inert dark: variants in kept
  ui components; theme switching is data-theme based (4 themes intact)
- first-frame inline theme script in index.html (reads namespaced key
  with legacy fallback, resolves system, sets color-scheme) - no flash
- consolidate duplicated db-type brand colors into lib/constants.ts
  single source (dbTypeColorMap + dbTypeBrandColorMap, with pg/mongodb
  aliases); instance health stroke now uses theme tokens
- verified via browser: dark #0d1117 / light #f5f6f8 both resolve,
  tokens cascade correctly

frontend/tailwind.config.js

@@ -1,55 +1,46 @@
 /** @type {import('tailwindcss').Config} */
 module.exports = {
-  darkMode: ["class"],
+  // 多主题经 data-theme 属性切换（--dg-* 单源），无 class 暗色模式
   content: ['./index.html', './src/**/*.{js,ts,jsx,tsx}'],
   theme: {
     extend: {
       colors: {
-        border: "hsl(var(--border))",
-        input: "hsl(var(--input))",
-        ring: "hsl(var(--ring))",
-        background: "hsl(var(--background))",
-        foreground: "hsl(var(--foreground))",
+        // 语义色全部派生自 --dg-* 设计 Token（唯一手写源）
+        border: "var(--dg-border)",
+        input: "var(--dg-border)",
+        ring: "var(--dg-blue)",
+        background: "var(--dg-bg-primary)",
+        foreground: "var(--dg-text-primary)",
         primary: {
-          DEFAULT: "hsl(var(--primary))",
-          foreground: "hsl(var(--primary-foreground))",
+          DEFAULT: "var(--dg-blue)",
+          foreground: "#ffffff",
         },
         secondary: {
-          DEFAULT: "hsl(var(--secondary))",
-          foreground: "hsl(var(--secondary-foreground))",
+          DEFAULT: "var(--dg-bg-tertiary)",
+          foreground: "var(--dg-text-primary)",
         },
         destructive: {
-          DEFAULT: "hsl(var(--destructive) / <alpha-value>)",
-          foreground: "hsl(var(--destructive-foreground) / <alpha-value>)",
+          DEFAULT: "var(--dg-red)",
+          foreground: "#ffffff",
         },
         muted: {
-          DEFAULT: "hsl(var(--muted))",
-          foreground: "hsl(var(--muted-foreground))",
+          DEFAULT: "var(--dg-bg-tertiary)",
+          foreground: "var(--dg-text-muted)",
         },
         accent: {
-          DEFAULT: "hsl(var(--accent))",
-          foreground: "hsl(var(--accent-foreground))",
+          DEFAULT: "var(--dg-bg-hover)",
+          foreground: "var(--dg-text-primary)",
         },
         popover: {
-          DEFAULT: "hsl(var(--popover))",
-          foreground: "hsl(var(--popover-foreground))",
+          DEFAULT: "var(--dg-bg-secondary)",
+          foreground: "var(--dg-text-primary)",
         },
         card: {
-          DEFAULT: "hsl(var(--card))",
-          foreground: "hsl(var(--card-foreground))",
-        },
-        sidebar: {
-          DEFAULT: "hsl(var(--sidebar-background))",
-          foreground: "hsl(var(--sidebar-foreground))",
-          primary: "hsl(var(--sidebar-primary))",
-          "primary-foreground": "hsl(var(--sidebar-primary-foreground))",
-          accent: "hsl(var(--sidebar-accent))",
-          "accent-foreground": "hsl(var(--sidebar-accent-foreground))",
-          border: "hsl(var(--sidebar-border))",
-          ring: "hsl(var(--sidebar-ring))",
+          DEFAULT: "var(--dg-bg-secondary)",
+          foreground: "var(--dg-text-primary)",
         },
       },
-      borderRadius: {
+borderRadius: {
         xl: "calc(var(--radius) + 4px)",
         lg: "var(--radius)",
         md: "calc(var(--radius) - 2px)",
@@ -59,25 +50,6 @@ module.exports = {
       boxShadow: {
         xs: "0 1px 2px 0 rgb(0 0 0 / 0.05)",
       },
-      keyframes: {
-        "accordion-down": {
-          from: { height: "0" },
-          to: { height: "var(--radix-accordion-content-height)" },
-        },
-        "accordion-up": {
-          from: { height: "var(--radix-accordion-content-height)" },
-          to: { height: "0" },
-        },
-        "caret-blink": {
-          "0%,70%,100%": { opacity: "1" },
-          "20%,50%": { opacity: "0" },
-        },
-      },
-      animation: {
-        "accordion-down": "accordion-down 0.2s ease-out",
-        "accordion-up": "accordion-up 0.2s ease-out",
-        "caret-blink": "caret-blink 1.25s ease-out infinite",
-      },
     },
   },
   plugins: [require("tailwindcss-animate")],