fix: Sensor tiles — move channel label to bottom-right, smaller

Channel chip (ch2) was inline with the label, stealing horizontal
space and causing label truncation ('Temper...'). Now positioned as
a tiny 9px label anchored bottom-right of the tile, giving the full
width to the metric label and value.

lib/widgets/sensors/sensor_telemetry_card.dart

@@ -2251,7 +2251,9 @@ class SensorMetricTile extends StatelessWidget {
         border: Border.all(color: data.accent.withValues(alpha: 0.14)),
       ),
       child: data.mapLocation == null || !allowMapPreview
-          ? Row(
+          ? Stack(
+              children: [
+                Row(
                   crossAxisAlignment: CrossAxisAlignment.start,
                   children: [
                     _MetricIcon(accent: data.accent, icon: data.icon),
@@ -2260,6 +2262,21 @@ class SensorMetricTile extends StatelessWidget {
                       child: _MetricText(data: data, keyPrefix: keyPrefix),
                     ),
                   ],
+                ),
+                if (data.channel != null)
+                  Positioned(
+                    right: 0,
+                    bottom: 0,
+                    child: Text(
+                      'ch${data.channel}',
+                      style: TextStyle(
+                        fontSize: 9,
+                        fontWeight: FontWeight.w700,
+                        color: data.accent.withValues(alpha: 0.5),
+                      ),
+                    ),
+                  ),
+              ],
             )
           : Column(
               crossAxisAlignment: CrossAxisAlignment.start,
@@ -2395,11 +2412,7 @@ class _MetricText extends StatelessWidget {
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
-        Row(
+        Text(
-          crossAxisAlignment: CrossAxisAlignment.start,
-          children: [
-            Expanded(
-              child: Text(
           data.label,
           maxLines: 1,
           overflow: TextOverflow.ellipsis,
@@ -2408,27 +2421,6 @@ class _MetricText extends StatelessWidget {
             fontWeight: FontWeight.w700,
           ),
         ),
-            ),
-            if (data.channel != null) ...[
-              const SizedBox(width: 8),
-              Container(
-                key: ValueKey('${keyPrefix}_channel_${data.fieldKey}'),
-                padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
-                decoration: BoxDecoration(
-                  color: data.accent.withValues(alpha: 0.12),
-                  borderRadius: BorderRadius.circular(999),
-                ),
-                child: Text(
-                  'ch${data.channel}',
-                  style: Theme.of(context).textTheme.labelSmall?.copyWith(
-                    color: data.accent,
-                    fontWeight: FontWeight.w800,
-                  ),
-                ),
-              ),
-            ],
-          ],
-        ),
         const SizedBox(height: 4),
         Text(
           data.value,