Solis Hybrid S: fix power decoding

[premultiply]

The battery power calculation was updated to correctly handle both firmware variants of the Solis Hybrid (S Series) inverter:

Before: Register 33149 was read as uint32. When the firmware reports a negative value as a signed 32-bit integer (e.g. 0xFFFFFC7C = −900 W during discharge), this was misinterpreted as ~4,295 MW — a classic 32-bit unsigned overflow.

After: Register 33149 is now read as int32, and its absolute value is taken via calc + abs. The sign is then applied separately by multiplying with +1 or −1 derived from the direction register 33135.

power = abs(int32(reg 33149)) × ((reg 33135 × 2) − 1)

This handles both known firmware variants:

• Firmware that stores battery power as a plain uint32 (always positive) with direction in register 33135 → abs(uint32) is identical to the raw value, sign applied via register 33135 ✓
• Firmware that stores battery power as a signed int32 (negative = discharge, as seen in issue Ginlog Solis Hybrid inverter : Incorrect power values (32-bit overflow) when battery is discharging + Modbus timeouts #28732) → abs(int32) strips the sign correctly, which is then re-applied from register 33135 ✓

Fixes #28732

[sourcery-ai]

Hey - I've left some high level feedback:

• Consider how the abs operation behaves for int32 on the minimum value (-2^31); if the calc engine doesn't guard against abs(INT32_MIN) overflow, explicitly clamping or converting to a larger numeric type before abs may be safer.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Consider how the `abs` operation behaves for `int32` on the minimum value (`-2^31`); if the calc engine doesn't guard against `abs(INT32_MIN)` overflow, explicitly clamping or converting to a larger numeric type before `abs` may be safer.

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Pull request overview

Updates the Solis Hybrid (S Series) meter template’s battery power calculation to correctly interpret register 33149 across firmware variants by decoding it as int32 and applying abs() before applying the charge/discharge direction from register 33135.

Changes:

• Change battery power register 33149 decoding from uint32 to int32.
• Wrap battery power in a calc + abs stage before multiplying by the direction-derived sign.