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>

tests/test_addon_translations.py

@@ -304,11 +304,19 @@ class Editor(unittest.IsolatedAsyncioTestCase):
             i18n.set_screens('xx', 'point')
             async with TestClient(TestServer(create_app(manager, True))) as client:
                 csrf = (await (await client.get('/api/inventory?light=1')).json())['csrf']
+                # Firmware from before the languages speaks English, whatever the screens' language is.
                 answer = await client.post('/api/screens/text.screen/identify', headers={'X-Screen-CSRF': csrf})
                 self.assertEqual(answer.status, 200)
-            action, data = ha.calls[0]
-            self.assertEqual((action, data['title'], data['subtitle'], data['button_text']),
-                             ('esphome.office_1_show_alert', '[xx] This is Office 1', '[xx] Identify, from ESP Screens', '[xx] OK'))
+                # Firmware that says it speaks the screens' language gets the card in it.
+                ha.registry = ha.registry + [{'entity_id': 'sensor.language', 'platform': 'esphome', 'original_name': 'Screen language',
+                                              'device_id': 'd1'}]
+                ha.states['sensor.language'] = {'state': 'xx'}
+                answer = await client.post('/api/screens/text.screen/identify', headers={'X-Screen-CSRF': csrf})
+                self.assertEqual(answer.status, 200)
+            texts = [(action, data['title'], data['subtitle'], data['button_text']) for action, data in ha.calls]
+            self.assertEqual(texts, [('esphome.office_1_show_alert', 'This is Office 1', 'Identify, from ESP Screens', 'OK'),
+                                     ('esphome.office_1_show_alert', '[xx] This is Office 1', '[xx] Identify, from ESP Screens', '[xx] OK')])
+            i18n.set_screens('en', 'point')
 
     async def test_a_tile_event_answers_home_assistant_in_english(self):
         with tempfile.TemporaryDirectory() as tmp, Language('addon.'):