Update secrets.yaml with negative price fee multiplier

Added provider fee multiplier for negative spot prices.

secrets.yaml

@@ -32,13 +32,21 @@ eprices_timezone: "Europe/Ljubljana"
 # Full list: https://api.energy-charts.info/
 eprices_country_bzn: "SI"
 
-# --- Provider fee multiplier ---
+# --- Provider fee multiplier for POSITIVE spot prices ---
 # Added on top of the raw spot price to account for your energy provider's fee.
 # Value is a DECIMAL MULTIPLIER, not a percentage.
 # Example: 0.12 means 12% provider fee added to the spot price.
 # Use decimal DOT, not comma (correct: 0.12 | wrong: 0,12).
 eprices_prov_fee: "0.12"
 
+# --- Provider fee multiplier for NEGATIVE spot prices ---
+# When the market spot price is negative, the provider pays you a share of
+# the negative price. This value is the fraction the provider keeps.
+# Example: 0.30 means provider keeps 30%, pays you 70% of the negative price.
+# Example: 0.00 means provider passes the full negative price to you (no fee).
+# Use decimal DOT, not comma (correct: 0.30 | wrong: 0,30).
+eprices_neg_prov_fee: "0.30"
+
 # --- VAT rate multiplier ---
 # Value added to the price to account for Value Added Tax in your country.
 # Value is a DECIMAL MULTIPLIER, not a percentage.