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/homeview.py

@@ -582,6 +582,8 @@ def build_plan(c, now, shadow, running, held=False, settled=True):
         cyc, waits = maintenance_runs(c, day0, day1, now, shadow)
         runs += cyc
         lines += waits
+        if getattr(c, "price_gap", False):
+            lines.append(line_no_prices(c.price_gap_since, now))
         runs += peak_run(c, day0, day1, now, shadow, limit_w)
         if c.p1_enabled:
             # The guard's ceiling: the cap, or this month's peak once above it.
@@ -1268,6 +1270,13 @@ def line_cycle_waits(name) -> str:
     return _t("cycle_waits", name=name)
 
 
+def line_no_prices(since, now) -> str:
+    """PRICE-01: no price covers now. `since` is an instant or None."""
+    if since is None:
+        return _t("no_prices_yet")
+    return _t("no_prices_since", at=messages.since_text(brussels(since), brussels(now)))
+
+
 def line_peak_limit(limit_w, shadow) -> str:
     return _w(shadow, "step_in", kw=_kw(limit_w))
 
@@ -1387,6 +1396,12 @@ def _samples() -> list:
             ("plan", run_house_why()), ("plan", run_house_why(True)),
             ("plan", run_house_amount()),
             ("plan", line_cycle_waits("Battery B")),
+            ("plan", line_no_prices(None, datetime(2026, 10, 14, 9, 0,
+                                                   tzinfo=timezone.utc))),
+            ("plan", line_no_prices(datetime(2026, 10, 13, 22, 0,
+                                             tzinfo=timezone.utc),
+                                    datetime(2026, 10, 14, 9, 0,
+                                             tzinfo=timezone.utc))),
             ("plan", line_prices(0.16, {"eur_kwh": 0.14, "label": "13:00"},
                                  {"eur_kwh": 0.36, "label": "19:00"})),
             ("plan", line_prices(None, None, None)),