feat: add light/dark theme toggle

- Implement theme state management
- Add CSS variables for both light and dark modes
- Create theme toggle button with Moon/Sun icons
- Sync Monaco editor theme with app theme
- Default to light theme with easy switching

Author: matheuscamposmt

src/index.css

@@ -4,6 +4,41 @@
 @custom-variant dark (&:is(.dark *));
 
 :root {
+    --background: oklch(0.98 0 0);
+    --foreground: oklch(0.15 0 0);
+    --card: oklch(1 0 0);
+    --card-foreground: oklch(0.15 0 0);
+    --popover: oklch(1 0 0);
+    --popover-foreground: oklch(0.15 0 0);
+    --primary: oklch(0.45 0.15 220);
+    --primary-foreground: oklch(0.98 0 0);
+    --secondary: oklch(0.92 0 0);
+    --secondary-foreground: oklch(0.15 0 0);
+    --muted: oklch(0.92 0 0);
+    --muted-foreground: oklch(0.45 0 0);
+    --accent: oklch(0.95 0 0);
+    --accent-foreground: oklch(0.15 0 0);
+    --destructive: oklch(0.55 0.22 25);
+    --destructive-foreground: oklch(0.98 0 0);
+    --border: oklch(0.88 0 0);
+    --input: oklch(0.96 0 0);
+    --ring: oklch(0.45 0.15 220);
+    --radius: 0.375rem;
+    --sidebar: oklch(0.97 0 0);
+    --sidebar-foreground: oklch(0.25 0 0);
+    --sidebar-primary: oklch(0.45 0.15 220);
+    --sidebar-primary-foreground: oklch(0.98 0 0);
+    --sidebar-accent: oklch(0.94 0 0);
+    --sidebar-accent-foreground: oklch(0.15 0 0);
+    --sidebar-border: oklch(0.88 0 0);
+    --sidebar-ring: oklch(0.45 0.15 220);
+    --success: oklch(0.45 0.18 150);
+    --warning: oklch(0.55 0.18 85);
+    --editor-bg: oklch(0.99 0 0);
+    --editor-line: oklch(0.96 0 0);
+}
+
+.dark {
     --background: oklch(0.12 0 0);
     --foreground: oklch(0.95 0 0);
     --card: oklch(0.15 0 0);
@@ -23,7 +58,6 @@
     --border: oklch(0.25 0 0);
     --input: oklch(0.22 0 0);
     --ring: oklch(0.75 0.15 220);
-    --radius: 0.375rem;
     --sidebar: oklch(0.1 0 0);
     --sidebar-foreground: oklch(0.85 0 0);
     --sidebar-primary: oklch(0.75 0.15 220);