Set confidence threshold to 80% and remove slider from frontend

✅ Frontend Changes:
- Removed confidence threshold slider from web interface
- Added fixed 80% confidence display with green info box
- Updated JavaScript to use fixed 0.8 threshold
- Removed slider-related CSS styles

✅ Backend Changes:
- Updated all API endpoints to default to 80% confidence (0.8)
- Modified POST /detect, GET /detect/hardcoded, POST /detect/base64
- Updated comments to reflect new default threshold

✅ Testing Updates:
- Updated test_api.py to use 80% confidence for all tests
- Ensures consistent testing with new threshold

✅ Benefits:
- High precision mode (80% confidence) reduces false positives
- Simplified user interface without threshold adjustment
- Consistent detection behavior across all endpoints

static/style.css

@@ -186,22 +186,18 @@ header p {
     border-radius: 8px;
 }
 
-.confidence-control {
+.confidence-info {
     margin-bottom: 15px;
+    padding: 10px;
+    background: #e8f5e8;
+    border-radius: 6px;
+    border-left: 4px solid #28a745;
 }
 
-.confidence-control label {
-    display: block;
-    margin-bottom: 8px;
-    font-weight: 500;
-}
-
-.confidence-control input[type="range"] {
-    width: 100%;
-    height: 6px;
-    border-radius: 3px;
-    background: #ddd;
-    outline: none;
+.confidence-info p {
+    margin: 0;
+    color: #155724;
+    font-size: 0.9rem;
 }
 
 .results-content {