Release fw 0.8.4: doc sync, System UI, BT/FM polish.

Align README, manual, and backlog to 0.8.4; add Web UI System tab for OTA/DSP uploads, serial in health header, FM seek down, and BT1035 paired list plus auto-reconnect API.

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/main/hardware_bootstrap.cpp

@@ -133,6 +133,10 @@ std::expected<void, HardwareBootError> HardwareBootstrap::boot()
         ESP_LOGW(kTag, "BT1035 device name set failed");
     }
 
+    if (auto reconnectResult = gBt1035.setAutoReconnect(3U); !reconnectResult) {
+        ESP_LOGW(kTag, "BT1035 auto-reconnect set failed");
+    }
+
     gReady = true;
     ESP_LOGI(kTag, "companion chips ready");
     return {};