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/web.py

@@ -43,7 +43,7 @@ from datetime import datetime, timezone
 
 from aiohttp import web
 
-from . import messages, selfconfig, uipage
+from . import messages, selfconfig, uipage, uitext
 from .haentities import EntityCache
 from .homeview import region_of
 from .validate import config_notes, setup_checks
@@ -54,13 +54,12 @@ from .uimodel import DeriveError, options_to_ui
 _LOG = logging.getLogger("goodwe.web")
 
 # 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/en.json. They are
+# app.css, app.js - plus the page words from app/ui_text/<lang>.json (English
+# and, since P5, Dutch; the page picks by the browser's language). They are
 # joined into ONE response here, once, so the page needs no second request
 # and no route of its own: the route list below is unchanged, and every URL
 # the page uses stays relative (ingress). No build step, no external file.
 STATIC = os.path.join(os.path.dirname(os.path.abspath(__file__)), "static")
-UI_TEXT = os.path.join(os.path.dirname(os.path.abspath(__file__)), "ui_text",
-                       "en.json")
 
 
 def _read(path):
@@ -71,7 +70,8 @@ def _read(path):
 def page() -> str:
     """The assembled index page. `</` is escaped inside the two inline
     scripts, so no text in them can close the tag early."""
-    ui_text = json.dumps(json.loads(_read(UI_TEXT)), ensure_ascii=False)
+    ui_text = json.dumps({lang: uitext.raw(lang) for lang in uitext.LANGS},
+                         ensure_ascii=False)
     scripts = {}
     for name in ("app.js", "settings.js"):
         scripts[name] = _read(os.path.join(STATIC, name))
@@ -129,8 +129,12 @@ def build_app(controller, selfcfg=None) -> web.Application:
     async def index(_request):
         return web.Response(text=index_page, content_type="text/html")
 
-    async def status(_request):
-        return web.json_response(controller.status_payload())
+    async def status(request):
+        # UX-13 P5: Home's sentences in the page's language, English or Dutch.
+        lang = uitext.lang_of(request.query.get("lang"))
+        if lang == "en":
+            return web.json_response(controller.status_payload())
+        return web.json_response(controller.status_payload(lang=lang))
 
     async def action(request):
         try:
@@ -264,7 +268,9 @@ def build_app(controller, selfcfg=None) -> web.Application:
         if model is not None:
             payload["messages"] = (
                 uipage.derive_messages(errors, problems, notes, model,
-                                       _keys_of(options)) if errors
+                                       _keys_of(options),
+                                       uitext.lang_of(_body.get("lang")))
+                if errors
                 else uipage.anchors(problems, notes, model, _keys_of(options)))
             payload["steps"] = uipage.step_problems(payload["messages"], model)
         if _body.get("setup"):
@@ -316,7 +322,8 @@ def build_app(controller, selfcfg=None) -> web.Application:
         except DeriveError:
             model = posted["model"]
             _opts, errors = uipage.to_options_partial(model, stored_now)
-            messages_ = [uipage.derive_message(e) for e in errors]
+            lang = uitext.lang_of(posted.get("lang"))
+            messages_ = [uipage.derive_message(e, lang) for e in errors]
             return web.json_response(
                 {"kind": "invalid", "problems": [], "by_key": {},
                  "unanchored": [], "messages": messages_,