Tasmota: Eable SML-IR reader phase readings

[thierolm]

Fix #26857

Eable SML-IR reader phase readings.
Refer to #26857.

[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• In Connection.Currents, the SML branch returns Voltage_L1/2/3 instead of Current_L1/2/3, which looks like a copy-paste bug and will surface as incorrect current readings when SML is available.
• The decorateTasmota switch has become quite complex with many condition combinations for currents/voltages/powers; consider refactoring to build up the embedded interfaces incrementally to avoid a combinatorial explosion of cases and make future extensions safer.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In `Connection.Currents`, the SML branch returns `Voltage_L1/2/3` instead of `Current_L1/2/3`, which looks like a copy-paste bug and will surface as incorrect current readings when SML is available.
- The `decorateTasmota` switch has become quite complex with many condition combinations for currents/voltages/powers; consider refactoring to build up the embedded interfaces incrementally to avoid a combinatorial explosion of cases and make future extensions safer.

## Individual Comments

### Comment 1
<location> `meter/tasmota/connection.go:220-226` </location>
<code_context>
 	return res.StatusSNS.Energy.Total + res.StatusSNS.SML.TotalIn, err
 }

-// Currents implements the api.PhaseCurrents interface
-func (c *Connection) Currents() (float64, float64, float64, error) {
-	return c.getPhaseValues(func(s StatusSNSResponse) Channels {
-		return s.StatusSNS.Energy.Current
-	})
+// Powers implements the api.PhasePowers interface
+func (c *Connection) Powers() (float64, float64, float64, error) {
+	s, err := c.statusSnsG.Get()
+	if err != nil {
+		return 0, 0, 0, err
+	}
+	if s.StatusSNS.SML.TotalIn != 0 {
+		// SML powers available
+		return float64(s.StatusSNS.SML.Power_L1), float64(s.StatusSNS.SML.Power_L2), float64(s.StatusSNS.SML.Power_L3), nil
</code_context>

<issue_to_address>
**issue (bug_risk):** SML branch of Currents returns voltage fields instead of current fields

In the SML branch, the code currently returns `Voltage_L1/L2/L3` instead of `Current_L1/L2/L3`, which will produce wrong current values whenever SML data is used. This appears to be a copy/paste mistake and should be updated to:

```go
if s.StatusSNS.SML.TotalIn != 0 {
    // SML currents available
    return s.StatusSNS.SML.Current_L1, s.StatusSNS.SML.Current_L2, s.StatusSNS.SML.Current_L3, nil
}
```
</issue_to_address>

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[andig]

why is usage necessary here? shouldn't this only check if the measurements are available?

[thierolm]

There are different device configurations possible with tasmota software. In case a tasmota device was configured to only measure a single phase / one channel for pv, battery, charger usage, I wanted to skip the phase api decoration.
Only in case the meter is configured to meter 3 channels/phases the phase apis should provide information.

[thierolm]

@andig imho the PR should be ready for merge.