Add multi‑commodity support to device scheduler

[Ahmad-Wahid]

This PR combines all the work done so far on supporting:

• multi-commodity:
  • Add multi‑commodity support to device scheduler #1946 (this PR)
  • feat: Split flex-context settings by commodity for dynamic capacity scheduling #2172
  • Feature: flex-context per commodity as list #2235
• multi-feed stocks:
  • Feat: Support shared storage (multi‑feed stock) #2001

The PR description could use a rewrite, but for lack of time I point you to the descriptions of the above PRs.
The original description for this PR follows below, but I want to point out that this chain of PRs did not end up introducing a new gas-price field. Instead, gas prices can be modelled by wrapping whatever existing dict flex-context you have into a list, and extending that list with a second entry as follows:

{
  "flex-context":  [
    <your old dict flex-context>,
    {
      "commodity": "gas",
      "consumption-price": "<your gas price>"
    }
  ]
}

---

Original description

This PR adds initial support for multi‑commodity commitments (e.g. gas and electricity) in the device_scheduler, building on the grouped‑devices functionality. Flow commitments can now be tagged with a commodity, and EMS‑level flow constraints are applied per commodity by aggregating the relevant devices.

TODO

• Specify how commodity is encoded per device in the flex‑model
• Exclude non‑matching commodities (e.g. gas devices) from EMS electricity commitments
• Extend flex‑model schema with commodity metadata
• add gas-price field to flex-context
• set up gas commitment using gas-powered devices and gas-price
• Update scheduling.rst
• Add tutorial examples for multi‑commodity scheduling

closes https://github.com/SeitaBV/simulations/issues/987

[read-the-docs-community]

Documentation build overview

📚 flexmeasures | 🛠️ Build #33498682 | 📁 Comparing 022e5c0 against latest (2d528fb)

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31 files changed · + 7 added · ± 24 modified

+ Added

• _autodoc/AGGREGATE_CONSUMPTION.html
• _autodoc/AGGREGATE_PRODUCTION.html
• _autodoc/COMMODITY_FLEX_CONTEXT.html
• _autodoc/COMMODITY_FLEX_MODEL.html
• _autosummary/flexmeasures.data.services.scheduling_result.html
• tut/multi-commodity.html
• tut/multi-feed-storage.html

± Modified

• changelog.html
• genindex.html
• index.html
• py-modindex.html
• _autodoc/AGGREGATE_POWER.html
• _autodoc/CHARGING_EFFICIENCY.html
• _autodoc/CONSUMPTION_PRICE.html
• _autodoc/DISCHARGING_EFFICIENCY.html
• _autodoc/PRODUCTION.html
• _autodoc/PRODUCTION_PRICE.html
• and 14 more...

[Flix6x]

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