UX-45: Home price chart draws one bar per price step the add-on uses

With 15-minute prices the chart now has one bar per quarter (92/96/100),
not hour averages; hourly and static tariffs still draw one bar per hour.
Cheap and dear marks come from the kept priceruns result (battery modes
on) or the arbitrage verdict's two points (off), not a thirds split.
A missing quarter is an empty bar. Removes plan.average_tip (EN/NL).

Co-Authored-By: Claude <noreply@anthropic.com>

goodwe_controller/app/ui_text/en.json

@@ -66,8 +66,7 @@
       "estimate_tip": "estimate from yesterday",
       "none_tip": "No price known",
       "no_prices": {"description": "No prices for today, so the chart shows only the plan."},
-      "list": "The plan in words",
-      "average_tip": "hour average"
+      "list": "The plan in words"
     },
     "peak": {"name": "Peak limit", "this_month": "This month's peak", "limit": "Limit", "none": "None recorded yet", "unreadable": "Cannot be read now"},
     "attention": {"name": "Needs attention", "nothing": "Nothing to look at", "to_look": "to look at", "details": "Details", "alarm": "Alarm", "warning": "Warning", "info": "Info"},