UX-13 P5: Dutch text, STYLE check, DOCS screenshots, period editor

- app/ui_text/nl.json and app/uitext.py: every page word in Dutch, English
  fallback per key; the page picks by browser language. Home's sentences
  move into ui_text `home_words`, so /status?lang=nl builds them in Dutch.
- test_ui_text.py: EN/NL key and placeholder parity, STYLE limits, jargon
  lists for both languages, no inline details, untranslated Dutch caught.
  Shared rules moved unchanged to tools/style_rules.py.
- tools/ux13_screenshots.sh/.py: DOCS screenshots from the demo fixtures in
  headless Chromium; docs/img/ux13/. Battery modes (P3): no screenshot.
- "Other time windows": a list editor (ui.periods) that builds
  static_profile and names bad times, empty prices, overlaps and gaps.

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

goodwe_controller/app/uilayout.py

@@ -23,8 +23,9 @@ CHOICE, ENTITY, ENTITY_LIST, TOGGLE, SEGMENTED, SLIDER = (
     "choice", "entity", "entity_list", "toggle", "segmented", "slider")
 NUMBER, TEXT, SELECT, LOCKED, INVERTER_LIST, SOLAR_LIST = (
     "number", "text", "select", "locked", "inverter_list", "solar_list")
+PERIOD_LIST = "period_list"     # P5: time windows, each with its own price
 CONTROLS = (CHOICE, ENTITY, ENTITY_LIST, TOGGLE, SEGMENTED, SLIDER, NUMBER,
-            TEXT, SELECT, LOCKED, INVERTER_LIST, SOLAR_LIST)
+            TEXT, SELECT, LOCKED, INVERTER_LIST, SOLAR_LIST, PERIOD_LIST)
 # What an entity picker offers first. `power_w` is a power sensor the add-on
 # reads as watts with no unit conversion, so validate.py warns on a kW sensor.
 ENTITY_KINDS = ("power_w", "power", "energy", "pct", "number", "any")
@@ -154,6 +155,8 @@ GROUPS = (
                   show=(("ui.fallback", "==", "daynight"),), wizard=4),
             Field("ui.night_price", NUMBER, "€/kWh", step=0.01,
                   show=(("ui.fallback", "==", "daynight"),), wizard=4),
+            Field("ui.periods", PERIOD_LIST, "€/kWh", step=0.01,
+                  show=(("ui.fallback", "==", "custom"),), wizard=4),
         )),
         Part("selling", (
             # OPT-11: derived from the batteries' selling switches once battery