Fix Decap CMS preview pane dark mode text colors

Added specific rules for Preview pane elements to ensure
rendered markdown is readable on dark background.

Chronicler #66

admin/index.html

@@ -318,6 +318,57 @@
       background: var(--ff-frost);
     }
 
+    /* ═══════════════════════════════════════════════════════════
+       PREVIEW PANE - Rendered Markdown
+    ═══════════════════════════════════════════════════════════ */
+    
+    [class*="Preview"],
+    [class*="preview"],
+    [class*="WidgetPreview"],
+    [class*="PreviewPane"],
+    [class*="frame-content"] {
+      background: var(--ff-dark) !important;
+      color: var(--ff-text) !important;
+    }
+
+    [class*="Preview"] *,
+    [class*="preview"] *,
+    [class*="PreviewPane"] *,
+    [class*="WidgetPreview"] *,
+    [class*="frame-content"] * {
+      color: var(--ff-text) !important;
+    }
+
+    [class*="Preview"] h1,
+    [class*="Preview"] h2,
+    [class*="Preview"] h3,
+    [class*="Preview"] h4,
+    [class*="Preview"] h5,
+    [class*="Preview"] h6 {
+      color: var(--ff-frost) !important;
+    }
+
+    [class*="Preview"] a {
+      color: var(--ff-fire) !important;
+    }
+
+    [class*="Preview"] code,
+    [class*="Preview"] pre {
+      background: var(--ff-dark-light) !important;
+      color: var(--ff-frost) !important;
+    }
+
+    [class*="Preview"] blockquote {
+      border-left: 3px solid var(--ff-arcane) !important;
+      color: var(--ff-text-dim) !important;
+    }
+
+    /* iframe preview if Decap uses one */
+    iframe[class*="preview"],
+    iframe[class*="Preview"] {
+      background: var(--ff-dark) !important;
+    }
+
     /* ═══════════════════════════════════════════════════════════
        MISC
     ═══════════════════════════════════════════════════════════ */