Add switch platform to Vistapool

[fdebrus]

Proposed change

Adds the switch platform to the Vistapool integration. This is the first PR that lets users actually control their pool from Home Assistant instead of just observing it. Follow-up to the sensor PR (#168051) and the binary_sensor PR (#172234), per joostlek's "one platform per PR" guidance.

Switches exposed (per pool):

• Filtration — filtration.status toggle.
• Relay 1–4 — relays.relay{1-4}.info.onoff toggles for the four generic relay outputs. is_on ORs the writable onoff with the read-only status next to it, so the entity correctly reads "on" when the device is currently driving the relay regardless of how the toggle was last set.
• Electrolysis cover / Electrolysis boost — hidro.cover_enabled / hidro.cloration_enabled, gated on hasHidro.
• Heating climate — dynamic, gated on filtration.hasHeat (the "Climat" toggle under the HEAT slider in the Hayward app).
• Smart mode freeze — dynamic, gated on filtration.hasSmart (Smart-mode freeze protection).

Implementation notes

Same patterns as sensor.py and binary_sensor.py:

• VistapoolSwitchEntityDescription extends SwitchEntityDescription.
• Conditional entities use exists_path (single path or tuple) instead of inline if blocks.
• Iterates entry.runtime_data.coordinators.values() for multi-pool support.
• AddConfigEntryEntitiesCallback, PARALLEL_UPDATES = 1, translation_key-only naming, unique IDs via build_unique_id(description.key).

Writes go through aioaquarite's AquariteClient.set_value(pool_id, path, value). AquariteError is caught and re-raised as HomeAssistantError with a translated set_failed message, which moves the quality_scale.yaml action-exceptions rule from exempt to done.

Tests

tests/components/vistapool/test_switch.py covers:

• Default fixture: test_all_entities with snapshot_platform (pins every entity's registry entry + state).
• Relay status fallback (read-only status field is OR'd into is_on).
• Dynamic entity creation: heating_climate only when filtration.hasHeat is set; smart_mode_freeze only when filtration.hasSmart is set.
• Parametrized turn_on / turn_off round-trip through set_value with the correct (pool_id, path, value) args.
• Error path: AquariteError from the library is re-raised as HomeAssistantError.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue: #
• Link to documentation pull request: Vistapool: document switch platform home-assistant.io#45643
• Link to developer documentation pull request:
• Link to frontend pull request:

Checklist

• I understand the code I am submitting and can explain how it works.
• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.
• Any generated code has been carefully reviewed for correctness and compliance with project standards.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
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