Add DAB ANTCAP calibration and fix BT1035 boot banner timing

Extend the FM-only ANTCAP antenna-varactor override to DAB, mirroring the
existing mechanism end to end (driver, tuner, service, EEPROM storage,
HTTP API). Live sweep on real hardware found no ANTCAP value beating
auto-tune on the ensembles tested, so DAB stays on auto-tune by default.

Also fix BT1035 boot: the module's real boot banner doesn't appear until
~18-24s after RESET# releases, not the 3.5s previously waited; add a
2-attempt retry and a baud-rate probe fallback for diagnostics.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Software/main/antenna_calibration.cpp

@@ -0,0 +1,26 @@
+/**
+ * @file    antenna_calibration.cpp
+ * @brief   net::AntennaCalibration implementation over HardwareBootstrap.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "antenna_calibration.hpp"
+
+#include "hardware_bootstrap.hpp"
+
+namespace antenna_calibration {
+
+net::AntennaCalibration& bridge() noexcept
+{
+    static net::AntennaCalibration instance{
+        .save = &hardware::HardwareBootstrap::saveFmAntCapCalibration,
+        .saveDab = &hardware::HardwareBootstrap::saveDabAntCapCalibration,
+    };
+    return instance;
+}
+
+} // namespace antenna_calibration