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).

opendbc_repo/opendbc/car/fingerprints.py

@@ -1,5 +1,6 @@
 from opendbc.car.interfaces import get_interface_attr
 from opendbc.car.body.values import CAR as BODY
+from opendbc.car.byd.values import CAR as BYD
 from opendbc.car.chrysler.values import CAR as CHRYSLER
 from opendbc.car.ford.values import CAR as FORD
 from opendbc.car.gm.values import CAR as GM
@@ -56,6 +57,8 @@ def all_legacy_fingerprint_cars():
 
 # A dict that maps old platform strings to their latest representations
 MIGRATION = {
+  "BYD HAN EV 23": BYD.BYD_HAN_EV_23,
+  "BYD SEAL PERFORMANCE 2025": BYD.BYD_SEAL_PERFORMANCE_25,
   "ACURA ILX 2016 ACURAWATCH PLUS": HONDA.ACURA_ILX,
   "ACURA RDX 2018 ACURAWATCH PLUS": HONDA.ACURA_RDX,
   "ACURA RDX 2020 TECH": HONDA.ACURA_RDX_3G,