feat: environment widgets layout redesign with always-visible widgets

- Desktop: 4-in-a-row layout (30/20/20/30 distribution)
- Tablet: 2x2 grid layout
- Mobile: Stacked vertically
- All widgets show "No data available" state instead of being hidden
- Sun position calculates from clock, defaults to 6am/6pm
- Environment refresh changed from 5min to 1 hour

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

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

lib/shared/widgets/weather_widget.dart

@@ -26,10 +26,16 @@ class WeatherWidget extends StatelessWidget {
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
 
+    // Show "no data" state when no API data and no legacy data
+    if (apiData == null && data == null) {
+      if (compact) {
+        return _buildCompactNoData(context, colorScheme);
+      }
+      return _buildNoData(context, colorScheme);
+    }
+
     // Convert API data to local model, or use legacy data
-    final weather = apiData != null
-        ? _fromApiData(apiData!)
-        : (data ?? WeatherData.mock());
+    final weather = apiData != null ? _fromApiData(apiData!) : data!;
 
     if (compact) {
       return _buildCompact(context, colorScheme, weather);
@@ -180,6 +186,82 @@ class WeatherWidget extends StatelessWidget {
       ),
     );
   }
+
+  Widget _buildNoData(BuildContext context, ColorScheme colorScheme) {
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            // Header
+            Row(
+              children: [
+                Icon(
+                  Icons.wb_sunny_outlined,
+                  size: 20,
+                  color: colorScheme.onSurfaceVariant,
+                ),
+                const SizedBox(width: 8),
+                Text(
+                  'Weather',
+                  style: Theme.of(context).textTheme.titleSmall?.copyWith(
+                        color: colorScheme.onSurfaceVariant,
+                      ),
+                ),
+              ],
+            ),
+            const SizedBox(height: 24),
+            Center(
+              child: Column(
+                children: [
+                  Icon(
+                    Icons.cloud_off_outlined,
+                    size: 32,
+                    color: colorScheme.outline,
+                  ),
+                  const SizedBox(height: 8),
+                  Text(
+                    'No data available',
+                    style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                          color: colorScheme.outline,
+                        ),
+                  ),
+                ],
+              ),
+            ),
+            const SizedBox(height: 16),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _buildCompactNoData(BuildContext context, ColorScheme colorScheme) {
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
+        child: Row(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            Icon(
+              Icons.cloud_off_outlined,
+              size: 24,
+              color: colorScheme.outline,
+            ),
+            const SizedBox(width: 8),
+            Text(
+              '--',
+              style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                    color: colorScheme.outline,
+                  ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
 }
 
 class _DetailChip extends StatelessWidget {