Feature: embedded layout mode and schedule improvements

- Add layout-embedded class for nested entity selectors
- Simplified styling for embedded widgets (less padding, borders)
- Schedule toggle row with summary badges
- Summary badges show datetime range, weekly schedule, holiday count
- Flag fallback styling for countries without valid ISO codes
- Section hint margin after embedded entity selector
- Holiday countries group without modifiers section

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

sources/scss/components/_dropdown.scss

@@ -208,6 +208,29 @@
             height: 100%;
             object-fit: cover;
         }
+
+        &.result-flag {
+            width: 32px;
+            height: 24px;
+            border-radius: 2px;
+            box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.1);
+            background: transparent;
+
+            img {
+                object-fit: contain;
+            }
+
+            .flag-fallback {
+                display: flex;
+                align-items: center;
+                justify-content: center;
+                width: 100%;
+                height: 100%;
+                background: linear-gradient(135deg, #e8eaed 0%, #dadce0 100%);
+                font-size: 14px;
+                color: #5f6368;
+            }
+        }
     }
 
     .result-icon {