UX-54: a Forecast tab with the sun, the house and each battery's level, per hour

A new tab beside Home and Batteries for today and tomorrow: the solar
forecast, the solar measured so far, the house's expected use and each
battery's expected level, with the plan's own charge and give blocks under it.

- Blocks are Home's: today's are the plan's `runs`, tomorrow's come from the
  same builders (`homeview.runs_for()`), in the plan lines' words.
- The sun is what solarfc reads; a daily total is spread over the bell and the
  tab says so. The house is HouseProfile.estimator(), as the plan reads it.
- The level is new: `daycurve.curve()` gives each battery the role
  `modetrade.decide()` gives it and moves it hour by hour inside the plan's
  floor and ceiling. It is an estimate and counts on `solar_trust_pct`.
- Built on request (`GET forecast`), no Home Assistant call. Measured solar is
  kept per hour in memory from the reading control already takes.
- A part not known yet is a note: modes off, no forecast, learning, no
  forecast for tomorrow, a monthly cycle, no level, stopped, shadow.

No decision, command, timing or option key changes. Found, not changed:
`dayplan.plan()` over-counts a state-only forecast (DECISIONS/UX-54).

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

goodwe_controller/test_selfconfig.py

@@ -636,10 +636,12 @@ _app = web.build_app(FakeController(), FakeSupervisor())
 _routes = sorted({(r.method, r.get_info().get("path"))
                   for r in _app.router.routes() if r.method != "HEAD"})
 print("    " + "  ".join(f"{m} {p}" for m, p in _routes))
-check("the configuration surface adds five routes and UX-13 one GET, and "
-      "none touches the three that were there",
+check("the configuration surface adds five routes, UX-13 one GET and "
+      "UX-54 one more GET (the Forecast tab), and none touches the three "
+      "that were there",
       _routes == [("GET", "/"), ("GET", "/config"), ("GET", "/config/model"),
-                  ("GET", "/ha/entities"), ("GET", "/status"),
+                  ("GET", "/forecast"), ("GET", "/ha/entities"),
+                  ("GET", "/status"),
                   ("POST", "/action"), ("POST", "/config/restart"),
                   ("POST", "/config/save"), ("POST", "/config/validate")])
 _ents_src = io.open(os.path.join(HERE, "app", "haentities.py"),