feat: implement Tesla smart charging v3 for Zaptec

- Beregner manglende kWh baseret på SOC og charge limit
- Finder de billigste 15-min elspot-timer før deadline
- Starter/stopper opladning via switch.home_charging
- Tilføjer failsafe 1 time før deadline
- Håndterer connected_finished session reset automatisk
- Stopper opladning når charge limit er nået
- Fuld modulopdeling: input_datetime, templates, binary_sensors, automations

include/templates/tesla_charging.yaml

@@ -0,0 +1,16 @@
+- sensor:
+
+    - name: tesla_kwh_needed
+      unit_of_measurement: "kWh"
+      state: >
+        {% set capacity = 75 %}
+        {% set soc = states('sensor.snowywhite_battery')|float %}
+        {% set limit = states('number.snowywhite_charge_limit')|float %}
+        {{ ((limit - soc)/100 * capacity)|round(2) }}
+
+    - name: tesla_charge_hours_needed
+      unit_of_measurement: "h"
+      state: >
+        {% set power = 11 %}
+        {% set kwh = states('sensor.tesla_kwh_needed')|float %}
+        {{ (kwh / power)|round(2) }}