refactor: unify CSS color variables across public and admin

- Add new standardized color variables in variables.css:
  - Public/light theme: --bg-primary, --bg-secondary, etc.
  - Admin/dark theme: --admin-bg, --admin-bg-alt, --admin-text, etc.
  - Gradient colors: --gradient-start (#3C856C), --gradient-2 (#60ECB4), --gradient-3 (#E390FF), --gradient-4 (#9557B5)
  - Shared: --success, --error, --warning, --accent-primary, --accent-secondary
- Update all CSS files to use new variables
- Keep admin-specific variables for dark theme sections

public/assets/css/colors.css

@@ -3,19 +3,19 @@
    ============================================================ */
 
 /* Background colors */
---bg-primary: #000000;
---bg-secondary: #000000;
---bg-tertiary: #0d0d0d;
---bg-active: #1a1a1a;
+--bg-primary: #ffffff;
+--bg-secondary: #f5f5f5;
+--bg-tertiary: #e8e8e8;
+--bg-active: #d0d0d0;
 
 /* Text colors */
---text-primary: #ffffff;
---text-secondary: #a6a6a6;
---text-tertiary: #666666;
+--text-primary: #111111;
+--text-secondary: #666666;
+--text-tertiary: #999999;
 
 /* Border colors */
---border-primary: #737373;
---border-secondary: #404040;
+--border-primary: #ddd;
+--border-secondary: #ccc;
 
 /* Status colors */
 --success: #5cd69d;
@@ -25,5 +25,11 @@
 /* Accent colors */
 --accent-primary: #9557b5;
 --accent-secondary: #683d7f;
---accent-foreground: #000000;
---accent-muted: #25162d;
+--accent-foreground: #ffffff;
+--accent-muted: rgba(149, 87, 181, 0.12);
+
+/* Gradient colors */
+--gradient-start: #3C856C;
+--gradient-2: #60ECB4;
+--gradient-3: #E390FF;
+--gradient-4: #9557B5;