Parse Bluetooth RSSI from bluetoothctl output

- Capture RSSI from [CHG] Device XX:XX RSSI: -XX lines
- Update device RSSI in real-time as bluetoothctl reports changes
- Auto-refresh selected device panel when RSSI updates
- Preserve RSSI when merging device updates

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

templates/index.html

@@ -5957,6 +5957,10 @@
                 device.tracker = device.tracker || { name: findMyInfo.type };
             }
 
+            // Merge with existing device data to preserve RSSI if not in update
+            if (btDevices[device.mac] && !device.rssi && btDevices[device.mac].rssi) {
+                device.rssi = btDevices[device.mac].rssi;
+            }
             btDevices[device.mac] = device;
 
             // Track signal history for graphs
@@ -5971,6 +5975,11 @@
                 pulseSignal();
             }
 
+            // Update selected device panel if this device is selected
+            if (selectedBtDevice === device.mac) {
+                updateBtSelectedDevice(device);
+            }
+
             // Check for tracker following
             checkTrackerFollowing(device);