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>

docs/img/ux13/README.md

@@ -0,0 +1,9 @@
+# UX-13 screenshots
+
+Made from the real page by `goodwe_controller/tools/ux13_screenshots.sh`. Do not
+edit them by hand: run the script again.
+
+- `home-*.png`: Home, running, in Dutch, in shadow mode, at phone width, and in setup.
+- `settings-*.png`: Settings (Installer view), and the time-window editor with an overlap.
+- `setup-step-1*.png`: Setup, step 1.
+- Battery modes (the Batteries screen and the Simple view): not built yet (UX-13 P3), so no screenshot.