Notation like Home Assistant, each screen in its own language, and the language in every build

From the end-to-end test on the bench boards and an independent review:
- Units spaced as Home Assistant does (54% / 54 % in German and French, 18°, 21.5 °C), in the firmware and the app.
- Grouping from five digits where the language does (1234 but 12.345 in Spanish, Polish, Portuguese): the layout
  message carries group_min and percent_space; an unknown number style no longer refuses a layout.
- Automatic follows Home Assistant's own language for the clock and numbers, also without a translation (Swedish:
  24 hours, 1 234,5; pt-BR: 1.234,5): regions.json from the CLDR for all 63 languages Home Assistant offers.
- 12-hour clock: the top bar says 3:48 PM, the clock card 3:48 (not 03:48), Last runs follow the clock.
- The climate setpoint font has the decimal comma; the value fonts have ², ³ and µ (m³ was a box).
- Weather days: at most three letters without the dot (mié, sáb, czw); the screen took three bytes.
- Texts fall back per key through the base language (pt-BR -> pt -> en) in the firmware and the app.
- Each screen gets the app's words in the language its firmware speaks; firmware from before the languages gets
  English and its own letters, not boxes.
- set_language re-reads what it writes (indentation, comments, quoted keys, CRLF, !include) and every build writes
  the language first; the 24-hour pin no longer hits a fresh install and waits for the old clock switches.
- Tests: region and notation, plural parity with the C++ rules, set_language edge cases, the pin, PUT /api/language.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

components/smart_display/tile_controls.h

@@ -243,7 +243,7 @@ inline const char *binary_state_text(const std::string &device_class, bool on) {
 }
 // Status line beside a control panel: what Home Assistant shows under the name.
 inline std::string status_text(const Tile &t) {
-  auto d = t.domain(); char b[48];
+  auto d = t.domain();
   if (d == "climate") {
     std::string text = climate_action_text(t.extra().hvac_action);
     if (text.empty()) text = climate_mode_text(t.state);
@@ -252,13 +252,13 @@ inline std::string status_text(const Tile &t) {
   }
   if (d == "cover") {
     std::string text = cover_state_text(t.state);
-    if (std::isfinite(t.position)) { snprintf(b, sizeof(b), " · %d%%", (int) std::lround(t.position)); text += b; }
+    if (std::isfinite(t.position)) text += " · " + screen_text::percent((int) std::lround(t.position));
     return text;
   }
   if (d == "media_player") {
     const std::string &title = t.extra().media_title;
     std::string text = (t.state == "playing" || t.state == "paused") && !title.empty() ? title : media_state_text(t.state);
-    if (std::isfinite(t.volume) && (t.supported & feature::MEDIA_VOLUME_SET)) { snprintf(b, sizeof(b), " · %d%%", (int) std::lround(t.volume * 100)); text += b; }
+    if (std::isfinite(t.volume) && (t.supported & feature::MEDIA_VOLUME_SET)) text += " · " + screen_text::percent((int) std::lround(t.volume * 100));
     return text;
   }
   return {};