Feat: change toy tutorial to kW units

[BelhsanHmida]

Description

• Change flexmeasures add toy-account to create kW-scale tutorial power sensors.
• Change the toy account day-ahead price sensor from EUR/MWh to EUR/kWh.
• Keep tutorial price CSV values in EUR/MWh and load them with --unit EUR/MWh to demonstrate unit conversion.
• Change toy power flow sensors and schedules from MW-scale to kW-scale.
• Keep the toy site and battery physical power capacities in 500 kVA.
• Change the reporter tutorial grid connection capacity from 0.5 MW to 500 kW.
• Update toy tutorial docs, runnable tutorial scripts, and CI tutorial inputs for the new units.
• Add regression coverage for battery and reporter toy-account units.
• Added changelog item in documentation/changelog.rst

Look & Feel

CLI examples now show kW-scale toy assets and schedules, for example:

Created <Sensor 2: discharging, unit: kW res.: 0:15:00>
Created <Sensor 7: grid connection capacity, unit: kW res.: P1Y>

The rerun toy tutorial plots showed kW labels such as 500kW, 0kW, -500kW, and reporter headroom values around 300kW to 500kW.

Simplified schedule output:

Beliefs for Sensor 'discharging' (ID 2).
Data spans 12 hours and starts at 2026-06-05 07:00:00+01:00.
The time resolution (x-axis) is 15 minutes.

  500kW |        /\                         /\
        |       /  \                       /  \
    0kW |------/----\---------------------/----\-----
        |     /      \                   /      \
 -500kW |____/        \_________________/        \___
             06:00        09:00        12:00        15:00
             discharging (toy-battery)

Simplified reporter output:

Beliefs for Sensor 'headroom' (ID 8).
Data spans a day and starts at 2026-06-05 00:00:00+01:00.
The time resolution (x-axis) is 15 minutes.

  500kW |--------\                              /--------
  400kW |         \____                  ____/
  300kW |              \________________/
             00:00        06:00        12:00        18:00
             headroom (toy-battery)

How to test

run the Docker tutorial scripts in order against a fresh isolated stack:

./documentation/tut/scripts/run-tutorial-in-docker.sh fm1139-server-1
./documentation/tut/scripts/run-tutorial2-in-docker.sh fm1139-server-1
./documentation/tut/scripts/run-tutorial3-in-docker.sh fm1139-server-1
./documentation/tut/scripts/run-tutorial4-in-docker.sh fm1139-server-1
./documentation/tut/scripts/run-tutorial5-in-docker.sh fm1139-server-1

Further Improvements

• Regenerate and upload the external UI screenshots in the separate FlexMeasures/screenshots repository.

Related Items

Closes #1139.

---

Sign-off

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on code under GPL or other license that is incompatible with FlexMeasures

[Flix6x]

Nice, my two main comments are:

• to actually not change the toy battery and site power capacities from 500 kVA to 500 kW, and
• to keep the example price data in EUR/MWh, but just scale it to the EUR/kWh sensor unit by explicitly setting the --unit EUR/MWh CLI option of flexmeasures add beliefs.

Also a question: are there screenshots that would need to be updated in https://github.com/FlexMeasures/screenshots (maybe making FlexMeasures/screenshots#8 obsolete by now)?

[BelhsanHmida]

Nice, my two main comments are:

• to actually not change the toy battery and site power capacities from 500 kVA to 500 kW, and
• to keep the example price data in EUR/MWh, but just scale it to the EUR/kWh sensor unit by explicitly setting the --unit EUR/MWh CLI option of flexmeasures add beliefs.

Also a question: are there screenshots that would need to be updated in https://github.com/FlexMeasures/screenshots (maybe making FlexMeasures/screenshots#8 obsolete by now)?

yes that pr is obsolete.