OPT-11 P3: price runs per battery

Cheap and expensive hours as runs of consecutive firm price slots
(priceruns.py); each battery's role per tick from its mode (modetrade.py):
grid charging for Leftover solar / Cheap hours only, never Solar first;
holding for the expensive runs; selling per battery (pack_sell) above the
spread and the floor. The site trade is sized inside the modes (loop bound)
and the peak guard's headroom; a run edge reseeds the loop. Cheap hours only
and selling are enabled on the Batteries screen and in the HA select
(appended). The site Why row no longer says "held back" when the peak limit
pushes power up (F2). Modes off: byte-identical to 7a00f12 on the trade path.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

goodwe_controller/app/web.py

@@ -34,7 +34,8 @@ succeeds, so the page stops opening the wizard by itself (uipage.setup_needed).
 UX-15's setup-only mode serves these routes from `setuponly.SetupOnly`, which
 commands nothing; there `/action` answers 409.
 OPT-11 P1 adds two `/action` values, `pack_use` and `pack_mode`, which set one
-battery's on/off switch or mode in the store (Controller._pack_action). They
+battery's on/off switch or mode in the store (Controller._pack_action); P3 adds
+`pack_sell`, that battery's selling switch. They
 are the only actions that name a battery; the configuration routes still reach
 none of them.
 """
@@ -58,7 +59,7 @@ from .uimodel import DeriveError, options_to_ui
 _LOG = logging.getLogger("goodwe.web")
 
 # OPT-11: the per-battery actions, which name a battery and a value.
-PACK_ACTIONS = ("pack_use", "pack_mode")
+PACK_ACTIONS = ("pack_use", "pack_mode", "pack_sell")
 
 # UX-13 P1: the page lives in app/static/ as three files - index.html,
 # app.css, app.js - plus the page words from app/ui_text/<lang>.json (English