byd: add BYD car port (HAN EV 23 / Seal Performance 2025) with MADS support

Car port adapted from HotIce0/openpilot develop_byd_comma4 to sunnypilot's
opendbc API (CP_SP signatures, (ret, ret_sp) carstate returns):

- opendbc/car/byd/: interface, carstate, carcontroller, bydcan, values,
  fingerprints (BYD_SEAL_PERFORMANCE_25 with full 91-msg fingerprint)
- opendbc/dbc/byd_common.dbc
- Brand registration: car/values.py, car/fingerprints.py (+MIGRATION),
  car.capnp SafetyModel byd @35, torque_data/params.toml
- safety/modes/byd.h: SAFETY_BYD 35U with real TX checks (steer torque
  cmd checks, longitudinal accel checks), MADS LKAS button from
  PCM_BUTTONS (944), pcm_cruise_check, ESC vehicle_moving. MISRA clean.
- safety/tests/test_byd.py: 120 tests (stock + longitudinal variants)
- opendbc/sunnypilot/car/byd/mads.py: MadsCarState tracking the
  dedicated LKAS steering wheel button
- sunnypilot/mads/mads.py: allow_always for byd (dedicated LKAS button)
- panda: restore SConstruct/SConscript build system, rebuild
  panda_h7.bin.signed (TIZI) with SAFETY_BYD + MADS lateral gating

Known limitation: BYD_HAN_EV_23 fingerprint is a subset of the Seal's,
so HAN requires FINGERPRINT=BYD_HAN_EV_23 env var (live fingerprint
cannot distinguish it; Seal fingerprints natively).

panda/board/obj/gitversion.h

@@ -1,2 +1,2 @@
-extern const uint8_t gitversion[18];
-const uint8_t gitversion[18] = "DEV-unknown-DEBUG";
+extern const uint8_t gitversion[19];
+const uint8_t gitversion[19] = "DEV-de77c89c-DEBUG";

panda/board/obj/version

@@ -1 +1 @@
-DEV-unknown-DEBUG
+DEV-de77c89c-DEBUG