Add Dynamic Power Pricing (DPP) Support

[bullitt186]

Adds support for E3/DC's Dynamic Power Pricing feature, enabling battery charging optimization based on dynamic electricity prices.

Changes

• get_dpp_data() - Read current DPP status and configuration (enabled, price limit, target SOC, active months)
• set_dpp_battery_charging() - Configure DPP settings with optional parameters (enabled, price_limit, soc_target, months_active)
• RSCP protocol tags for battery DPP (taken over from @git-kick's iobroker integration)
• Example script under examples/dpp_example.py

Example

# Read settings
dpp_data = e3dc.get_dpp_data()

# Configure DPP
e3dc.set_dpp_battery_charging(
    enabled=True,
    price_limit=0.27,
    soc_target=80,
    months_active="JFMAmjjasOND"
)

Testing

Validated with black, flake8, pyright and tested on E3/DC S10X hardware.

Note: I tried to also integrate the Wallbox DPP control, but couldn't get it to work (didn't reflect the actually configured values on my S10X), so i left it out completely except for the RSCP tags.