feat: add Tibber feed-in tariff provider (#1189)

The `FeedInTariffTibber` provider requests `priceInfo` and `priceInfoRange` with
`resolution: QUARTER_HOURLY` and preserves the native 15-minute timestamps. It uses Tibber's
`energy` spot-price component without the `tax` part or EOS electricity-price charges. The
end-customer `total` component is deliberately ignored.

The provider deliberately rejects hourly API responses instead of silently repeating them. It
reuses `elecprice.tibber.access_token` and `elecprice.tibber.home_id`, so no duplicate credentials
are needed.

Signed-off-by: Andreas Schmitz <akkudoktor.net>
Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

docs/akkudoktoreos/prediction.md

@@ -223,6 +223,7 @@ Configuration options:
       them to the configured prediction horizon when necessary.
     - `FeedInTariffFixed`: Provides fixed feed in tariff values.
     - `FeedInTariffImport`: Imports from a file or JSON string or by endpoint data provision.
+    - `FeedInTariffTibber`: Retrieves Tibber's native quarter-hour energy-price component.
 
   - `energycharts.bidding_zone`: Bidding zone Energy Charts shall provide feed-in tariff for.
   - `feedintarifffixed.feed_in_tariff_kwh`: Fixed feed in tariff (€/kWh).
@@ -308,6 +309,25 @@ from the configuration may be reloaded. To avoid these issues, use the **PUT** e
 data and rely on file/JSON imports only for initial setup.
 :::
 
+### FeedInTariffTibber Provider
+
+The `FeedInTariffTibber` provider requests `priceInfo` and `priceInfoRange` with
+`resolution: QUARTER_HOURLY` and preserves the native 15-minute timestamps. It uses Tibber's
+`energy` spot-price component without the `tax` part or EOS electricity-price charges. The
+end-customer `total` component is deliberately ignored.
+
+The provider deliberately rejects hourly API responses instead of silently repeating them. It
+reuses `elecprice.tibber.access_token` and `elecprice.tibber.home_id`, so no duplicate credentials
+are needed.
+
+```json
+{
+  "feedintariff": {
+    "provider": "FeedInTariffTibber"
+  }
+}
+```
+
 ## Load Prediction
 
 Prediction keys: