Merge release/1.0 (TARIFF-03) into SAFETY-07

The anticipated conflict again, and only it: both cards prepend to CHANGELOG.md's
Unreleased section. Both entries kept, SAFETY-07 first. app/main.py and DOCS.md
auto-merged, so the overlap claim on #18 still holds - config.yaml and
validate.py remain untouched by this card even after TARIFF-02 and TARIFF-03
widened both.

Full suite green on the merge result, test_price.py and test_static_tariff.py
included.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015VXjA3LWccN1rJsk3okyPC

goodwe_controller/app/main.py

@@ -48,6 +48,7 @@ from .maintenance import IDLE, MaintConfig, Maintenance
 from .mqtt import MqttPublisher
 from . import peakguard
 from .p1 import P1Ingest, build_source, is_enabled
+from .static_tariff import static_status
 from .tariff import PeakStore, PeakTracker
 from .validate import ConfigRefused, refuse, validate_startup_config
 from .watchdog import SignWatchdog, SignWatchdogConfig, loop_is_following
@@ -227,6 +228,10 @@ class Controller:
         self.grid = self.soc = self.batt = None
         self.peak_fc = None
         self.cheap = False
+        # TARIFF-03. One line of prose for the status page saying WHICH tariff
+        # window we are in and why it is or is not cheap - so "Cheap window:
+        # no" is an evidenced answer rather than a bare no.
+        self.tariff_words = "no static profile"
         self.last_write = None
         self.last_write_at = None
         self.last_write_ok = None
@@ -280,9 +285,31 @@ class Controller:
             now_p = await self.hass.number(now_e)
             avg_p = await self.hass.number(avg_e)
             self.cheap = (now_p is not None and avg_p is not None and now_p <= avg_p)
+            self.tariff_words = "Home Assistant price entities"
         else:
-            # Fixed-tariff site: never force a paid grid top-up, wait for sun.
-            self.cheap = False
+            # TARIFF-03. §9.2 makes a static day/night tariff a first-class
+            # product, and its required EMS handling is TIME-WINDOW SHIFTING.
+            # The add-on has exactly one shiftable load in 0.5.x - the
+            # maintenance cycle's cheap-window grid top-up, ~15 lines below in
+            # cycle() - so this is where the window reaches something that moves
+            # energy. With `static_profile` empty this returns False and the
+            # behaviour is bit-for-bit what it has always been: "fixed-tariff
+            # site, never force a paid grid top-up, wait for sun".
+            #
+            # ⚠️ SYNCHRONOUS AND I/O-FREE, ON PURPOSE. The provider-backed
+            # resolver (static_tariff.resolve_tariff) can perform an HTTP fetch,
+            # and this coroutine is on the path that feeds the ESP32 heartbeat -
+            # a supplier's TLS timeout here would be a supplier able to push the
+            # add-on towards layer 1's 30 s veto. Generation from a static
+            # profile is pure arithmetic, so §2.3's "regenerate on the tick"
+            # applies and there is nothing to block on. Putting a fetched series
+            # on this path needs a BACKGROUND refresh and belongs with OPT-04.
+            #
+            # ⚠️ AND IT CANNOT BE BOTH. validate.py refuses static_profile
+            # alongside the two Home Assistant entities, because this `if` picks
+            # one and the loser is silent.
+            self.cheap, self.tariff_words = static_status(
+                o, datetime.now(timezone.utc))
 
         if self.inputs_ok:
             if self.inputs_bad_since is not None:
@@ -1215,6 +1242,7 @@ class Controller:
             ("Maintenance phase", self.maint.phase),
             ("Maintenance due", "now" if next_due is None else next_due.strftime("%Y-%m-%d")),
             ("Cheap window", "yes" if self.cheap else "no"),
+            ("Tariff", self.tariff_words),
         ]
         return {
             "banner": banner, "level": level, "rows": rows, "checks": checks,