[BUG] nominal_charging_capacity_kW refers to battery-side, not grid-side power — contradicts industry convention

[joda9]

Describe the bug

The naming convention for EV charging capacities in charging_processes_df is inverted compared to the standard industry/normative convention:

• nominal_charging_capacity_kW currently refers to the battery-side power (what the vehicle receives)
• grid_charging_capacity_kW is calculated as nominal / eta_cp, making it larger than the nominal value

Example with a standard 11 kW wallbox and eta_cp = 0.9:

• Current: nominal = 11 kW, grid = 12.22 kW
• Expected: nominal = 11 kW, grid = 11 kW, battery = 9.9 kW

In industry standards (DIN, IEC 61851, manufacturer datasheets), "nominal charging capacity" always refers to the grid-side AC power rating of the charging station. A "11 kW wallbox" draws 11 kW from the grid (3-phase, 16A, 230V) and delivers less to the vehicle battery due to losses in the onboard charger and cabling.

To Reproduce

1. Load SimBEV charging processes via import_electromobility() or from OEP table edut_00_174
2. Inspect charging_processes_df columns:

   edisgo.electromobility.charging_processes_df[
       ["nominal_charging_capacity_kW", "grid_charging_capacity_kW"]
   ]

3. Observe that grid_charging_capacity_kW > nominal_charging_capacity_kW for all rows
4. The relationship is grid = nominal / eta_cp (defined in electromobility.py:105-110)

Expected behavior

The naming should follow the standard convention:

Column	Meaning	Example (11 kW wallbox, eta=0.9)
nominal_charging_capacity_kW	Grid-side AC power (nameplate rating)	11.0 kW
battery_charging_capacity_kW	Battery-side DC power (after losses)	9.9 kW

The efficiency relationship should be:

battery = nominal * eta_cp    (not: grid = nominal / eta_cp)

Affected files

The following files use the current (inverted) convention and would need to be updated:

• edisgo/network/electromobility.py (lines 105-110, 443) — property definition and flexibility band calculation
• edisgo/io/electromobility_import.py (lines 34-45, 885-895, 1338-1356) — DataFrame columns, OEP import, private charging
• edisgo/flex_opt/charging_strategies.py (line 385) — grid load calculation: nominal / (1000 * eta_cp)
• OEP table edut_00_174 — column names charging_capacity_nominal and charging_capacity_grid

Additional context

• The current convention originates from SimBEV, which models charging from the vehicle perspective (SoC progression, charging duration) and then scales up to grid load
• The OEP table inherits this SimBEV convention