PRICE-01: price_service provider, fallback chain, and the gate read from it

A new price source, `price_provider: price_service`: the owner's price server,
one fixed HTTPS host, a bearer token (new password option
`price_service_token`), wholesale energy only so markup and taxes are added as
for generic_dayahead.

The chain is server, then energy-charts, then the prices the history store
kept. A step counts only if it has a price for now. Each step down and back up
is one log line. With every source down a site plans from what it saved.

No price for now: one status row, one Home plan line and one notification, in
English and Dutch, cleared when a price returns. With this provider the
maintenance charge gate reads the provider's prices and keeps the Home
Assistant rule: the current 15-minute price is at or below today's average.

The token is hidden on the settings page, refused when missing, and taken out
of any error text. Other providers, `off` and the Home Assistant pair take the
road they always took (scripted-day probe against 0ce7d35: one line differs,
the refusal that lists the known providers). See
DECISIONS/PRICE-01-own-price-server.md.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bdqr7PiaHcBnzPituu2yTC

goodwe_controller/translations/en.yaml

@@ -199,6 +199,9 @@ configuration:
   price_feed_url:
     name: "Tariff · Price feed URL override"
     description: "Leave it empty to use the source's own feed. An override is sent exactly as typed and often returns only one day."
+  price_service_token:
+    name: "Tariff · Price service token"
+    description: "For the price service only. The token you were given for it. Leave it empty with any other price source."
   price_horizon_h:
     name: "Tariff · Price look-ahead (hours)"
     description: "How many hours of prices to ask the source for."

goodwe_controller/translations/nl.yaml

@@ -180,6 +180,9 @@ configuration:
   price_feed_url:
     name: "Tarief · Afwijkende URL voor de prijsfeed"
     description: "Laat leeg om de eigen feed van de bron te gebruiken. Een afwijkende URL wordt letterlijk verstuurd en geeft vaak maar één dag terug."
+  price_service_token:
+    name: "Tarief · Token van de prijsdienst"
+    description: "Alleen voor de prijsdienst. Het token dat u ervoor kreeg. Laat leeg bij een andere prijsbron."
   price_horizon_h:
     name: "Tarief · Prijzen vooruit (uren)"
     description: "Hoeveel uur aan prijzen de add-on bij de bron opvraagt."