Fiat eDoblo: add BMS pack temperature polling

[strangesource]

Problem

The FTDO profile already polls BMS min/max cell voltage, HV voltage/current, SOH, and available energy, but standard BMS pack temperature metrics and average cell voltage remain empty.

Reproduction / observation

On the current FTDO vehicle profile, the following standard metrics are present but unset:

v.b.p.temp.avg
v.b.p.temp.max
v.b.p.temp.min
v.b.p.voltage.avg

A read-only UDS scan against the e-Berlingo BMS while v.e.on = yes showed the BMS supports these identifiers via 0x6b4 -> 0x694, UDS service 0x22:

D817 highest_temperature len=1 data=40  -> 24°C
D87D lowest_temperature  len=1 data=3f  -> 23°C
D877 average_temperature len=1 data=3f  -> 23°C
D43D avg_cell_voltage    len=2 data=0f56 -> 3.926V

CAN status remained clean after polling: no RX/TX errors, no overflows, no failed TX frames.

Root cause / code path

FTDO BMS diagnostic polling is defined in vehicle_ftdo_polls and decoded in OvmsVehicleFiatEDoblo::IncomingBatteryPoll(). The relevant BMS DIDs were simply not included/decoded yet.

Fix

Add BMS polling and decoding for:

• 0xd43d -> v.b.p.voltage.avg
• 0xd87d -> v.b.p.temp.min
• 0xd817 -> v.b.p.temp.max
• 0xd877 -> v.b.p.temp.avg

Also update FTDO docs and change history.

Validation performed

• Runtime read-only UDS validation on Citroën e-Berlingo / FTDO-compatible vehicle with v.e.on = yes.
• Confirmed target metrics were empty before implementation.
• Built firmware from clean origin/master branch:

cd vehicle/OVMS.V3
source ~/.espressif/ovms-idf-v3.3-env.sh
make BATCH_BUILD=1 defconfig SDKCONFIG_DEFAULTS=support/sdkconfig.default.hw31
make BATCH_BUILD=1 -j$(sysctl -n hw.ncpu)