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/config.yaml

@@ -556,6 +556,10 @@ options:
   # naming that consequence on every fetch that uses an override; clearing this
   # option is what restores the full horizon.
   price_feed_url: ""
+  # PRICE-01. The bearer token for the owner's price server
+  # (`price_provider: price_service`). A password field. Empty with any other
+  # source. Never printed: not in the log, the status page or a notification.
+  price_service_token: ""
   price_horizon_h: 48
   price_timeout_s: 10
 
@@ -1085,7 +1089,7 @@ schema:
   # this line offers exactly PROVIDERS + RETIRED_PROVIDERS + 'off' - derived, not
   # typed - and register() refuses to re-register a retired id, so the two
   # cannot both claim one.
-  price_provider: list(off|generic_dayahead|custom_formula|engie_dynamic|totalenergies_dynamic|eneco_eddy|manual_csv)
+  price_provider: list(off|generic_dayahead|price_service|custom_formula|engie_dynamic|totalenergies_dynamic|eneco_eddy|manual_csv)
   price_markup_eur_kwh: float(0,1)
   price_taxes_eur_kwh: float(0,1)
 
@@ -1119,6 +1123,7 @@ schema:
   price_formula: str?
   price_csv_path: str?
   price_feed_url: str?
+  price_service_token: password?
   price_horizon_h: int(1,72)
   price_timeout_s: int(2,60)
   price_now_entity: str?