Add configurable solar grid input start and tolerance numbers

[oehrn]

Summary

This PR introduces two new number entities to make previously hardcoded SmartMode thresholds configurable:

• solar_grid_input_start → controls SmartMode.POWER_START (min 25W, max 5000W)
• solar_grid_input_tolerance → controls SmartMode.POWER_TOLERANCE (min 5W, max start - 10W)

Both values are persisted via RestoreNumber and applied automatically on startup. The tolerance entity range updates dynamically whenever the start value changes.

UI labels/translations were added for en/de/fr/nl.

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How the new entities override the previous hardcoded defaults

Previously, the integration relied on static defaults in const.py:

• SmartMode.POWER_START = 50
• SmartMode.POWER_TOLERANCE = 5

These constants are referenced across the codebase:

• manager.py uses SmartMode.POWER_START for “start / kick-off” behavior (e.g., starting idle devices and enabling discharge of produced power).
• device.py uses SmartMode.POWER_TOLERANCE as the device-level deadband in power_charge() / power_discharge() (skip updates when the delta is within tolerance).

This PR adds two new persistent (RestoreNumber) manager-level entities:

• number.*_solar_grid_input_start → updates SmartMode.POWER_START
• number.*_solar_grid_input_tolerance → updates SmartMode.POWER_TOLERANCE

Runtime behavior

• On integration startup, const.py still provides fallback defaults (50W / 5W).
• The new number entities are created and initialized with these defaults.
• When Home Assistant restores the last saved entity states (RestoreEntity), the restored values are applied via the entity callbacks:
  • update_power_start(...) sets SmartMode.POWER_START
  • update_power_tolerance(...) sets SmartMode.POWER_TOLERANCE

As a result, the thresholds are no longer effectively hardcoded at runtime—they are overridden by the persisted HA entity values.

Constraints / clamping

• solar_grid_input_start: 25W … 5000W
• solar_grid_input_tolerance: 5W … (start - 10W)
  • The tolerance entity range is updated automatically when the start value changes.
  • If tolerance exceeds the allowed maximum, it is clamped and the entity state is updated to remain consistent.

Why keep the constants in const.py?

They serve as safe defaults for fresh installs (no restored state yet) and avoid refactoring all existing call sites that reference SmartMode.POWER_START / SmartMode.POWER_TOLERANCE.

[oehrn]

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