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/app/validate.py

@@ -1706,6 +1706,22 @@ def _price_problems(opts: dict, notes: list | None = None) -> list[str]:
             f"{S('price_csv_path')} is empty. Set the path to the CSV file, or "
             "choose 'off'.")
 
+    # PRICE-01. The price service answers only to its token. Without one every
+    # fetch is refused and the add-on lives on its fallbacks, which the
+    # operator would not see: a source they chose, overridden by a layer they
+    # cannot see. A token the server cannot read as a header is the same case.
+    if pid == "price_service":
+        token = str(opts.get("price_service_token", "") or "").strip()
+        if not token:
+            problems.append(
+                f"{S('price_provider')} is 'price_service', but "
+                f"{S('price_service_token')} is empty. Set the token, or "
+                "choose another source.")
+        elif any(c.isspace() or not c.isprintable() for c in token):
+            problems.append(
+                f"{S('price_service_token')} has a space or a line break in "
+                "it. Paste the token again, with nothing around it.")
+
     return problems