Fix patchy background: Remove color inconsistency between elements

Root cause found: Background color mismatch within the same app
- body/gradio-container: #fafafa
- .card/.card-content: white

This created visual inconsistency. Changed all elements to use consistent #fafafa background.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

app.py

@@ -477,7 +477,7 @@ with gr.Blocks(
             font-weight: 700 !important;
         }
         .card {
-            background: white !important;
+            background: #fafafa !important;
             border-radius: 12px !important;
             box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06) !important;
             border: 1px solid #e5e7eb !important;
@@ -511,7 +511,7 @@ with gr.Blocks(
             padding: 1.5rem !important;
             color: #4b5563 !important;
             line-height: 1.6 !important;
-            background: white !important;
+            background: #fafafa !important;
         }
         .stats-grid {
             display: grid !important;