feat(switch): ✨ add manual EVU2 input for models that do not report SG2

[rhammen]

🔍 What this fixes

The last open piece of #500 (step 3 of the plan agreed with @siedi in that thread).

On the MSW2-9S, the SmartGrid status can never show a state that needs the SG2 contact closed. The controller reacts to SG2 normally but reports it nowhere the integration can read:

• calc 185 ID_WEB_HZIO_EVU2 stays 0 whatever the contact does, confirmed by two owners (@Zaschii, SG2 wired permanently closed; @mhuiskes, SG2 switched by a relay);
• the RFV terminal that carries SG2 on Luxtronik 2.0 (Smart Grid Status always shows evu_locked on Luxtronik 2.0 (SG1.1) #669) reads 0.0 on these units.

The gate is an explicit model list rather than a data test. calc 185 reads 0 in all 84 dumps in the diagnostics corpus, SmartGrid on or not, so nothing in the data separates "contact open" from "contact not reported".

✨ Changes

Manual SG2 input

• New config switch EVU2 input (manual), on MSW2-9S units only (EVU2_MANUAL_INPUT_MODELS) and only while Smart Grid mode is not Off, the same rule as the SG offset numbers. Nothing is written to the heat pump.
• SG2 is now resolved in this order: RFV sign (Lux 2.0 wiring) > manual switch > calc 185. The SmartGrid status sensor and the EVU2 binary sensor share that resolver, so they always agree.
• The value lives on the coordinator and goes into each poll's data (LuxtronikCoordinatorData.evu2_manual, None when not applied). The switch shows the stored setting, not the applied value, so turning Smart Grid off and reloading does not store it as off.
• Restore across restarts is done by the coordinator before the platforms are set up, looked up by unique id. Restoring in the switch itself let the status publish a value computed from the default and then flip, a spurious state change on every restart. The restore is gated on the model alone, so turning SG on through the select (no reload) applies the stored setting. A disabled switch counts as SG2 open.

Diagnostics

• New derived section: evu2_manual (the setting) and evu2_manual_applied (what the status used, null when not applied). An MSW2-9S report is explainable from the dump alone now.

Entity attributes

• Entities without a register no longer carry luxtronik_key: "NSET UNSET" (the UNSET enum name sliced as if it were an index), and neither do luxtronik_key_* fields left at UNSET. On a live install that was six attributes across the water heater and both climate entities.
• The heating climate entity's luxtronik_key_current_temperature now names the key it actually reads (C0227, or the configured indoor sensor); base built the attribute before climate swapped the key in.

Docs

• ADVANCED_FEATURES.md: a how-to section for the switch (what on/off mean, the two wiring cases, Smart Grid on/off and reload behaviour, an example automation that copies an SG2 relay onto the switch), linked from the Smart Grid mode entry and the README.
• Translations in en/de/nl/cs/pl, icon.

🧪 Tests

• Resolver order, the model + SmartGrid gate, the per-poll apply, restore (including a renamed entity id, a disabled switch, SG off at startup then on at runtime, and asserting on the data the entities read rather than private state), setup-order before the platforms, the switch entity, the diagnostics section, and the attribute changes.
• Full run: 1370 passed, 1 skipped, coverage 100%. ruff check / format clean, basedpyright 0 errors, codespell clean, translation coverage complete.
• Reviewed in three rounds; the findings (restore applied one poll late, disabled switch still steering the status, runtime SG-on using the default, doc accuracy) are fixed in the commits above.
• Not tested on a real MSW2-9S: confirmation from @Zaschii / @mhuiskes on hardware is still needed, so this PR refers to Enhancement request: Smart Grid #500 rather than closing it.

Refs #500

🤖 Generated with Claude Code

[github-actions]

Package	Line Rate	Health
custom_components.luxtronik2	100%	✔
Summary	100% (3955 / 3955)	✔