feat: v0.4.0 - provider icon system, settings modal & polish

- Add provider icon system with extracted icon library (cc-switch based)

- Persist icon and icon_color in SQLite and config.toml

- Add Settings modal (theme / language / update check / silent download)

- Add useTheme and useUpdateCheck hooks

- Add provider icon picker (IconPicker) with search and grid

- Fix icon frame 2-layer color difference in ProviderEdit

- Dashboard heatmap and daily usage improvements

- Sessions page polish and adaptive layout

- Bump version to 0.4.0

tailwind.config.js

@@ -1,8 +1,29 @@
 /** @type {import('tailwindcss').Config} */
 export default {
   content: ["./index.html", "./src/**/*.{js,ts,jsx,tsx}"],
+  darkMode: ["class", ".dark"],
   theme: {
-    extend: {},
+    extend: {
+      colors: {
+        app: "var(--bg-app)",
+        panel: "var(--bg-panel)",
+        input: "var(--bg-input)",
+        hover: {
+          DEFAULT: "var(--bg-hover)",
+          2: "var(--bg-hover-2)",
+        },
+        footer: "var(--bg-footer)",
+        "cell-empty": "var(--bg-cell-empty)",
+        border: {
+          DEFAULT: "var(--border)",
+          strong: "var(--border-strong)",
+        },
+        content: {
+          primary: "var(--text-primary)",
+          muted: "var(--text-muted)",
+        },
+      },
+    },
   },
   plugins: [],
 };