Watch the feed by the declared keepalive and HA by the API link (0.2.26)

Since 0.2.20 the manager repeats a layout every 120 s, while the firmware
treated anything older than 95 s (sized for the original 25 s keepalive) as
stale: on a quiet screen every card read "Niet beschikbaar" and the header
"HA niet verbonden" for 25-45 s of each two-minute round, on both boards.

"HA niet verbonden" now follows ESPHome's own api_is_connected(); the feed
watchdog uses the cadence the layout message declares ("keepalive", seconds,
120 s when absent) and tolerates one missed round plus loop slack before
showing "ESP Screens niet actief". The tick redraws once when either flips.
Firmware 0.2.22 for CYD and Guition.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/test_extended.py

@@ -5,6 +5,7 @@ import tempfile
 import unittest
 from unittest.mock import patch
 sys.path.insert(0,str(Path(__file__).resolve().parents[1]/'screen_manager/app'))
+from server import KEEPALIVE_SECONDS
 from core import validate_layout, state_message, packets
 from firmware import Firmware
 from test_portal import ManagerTests
@@ -101,6 +102,7 @@ class SpecialTileSync(unittest.IsolatedAsyncioTestCase):
    await m.sync_one('text.screen',m.layouts['text.screen'])
    sent=[message for _,message in m.ha.messages]
    self.assertEqual(sent[0]['entities'],['screen.clock','sun.sun'])
+   self.assertEqual(sent[0]['keepalive'],KEEPALIVE_SECONDS,'the screen sizes its feed watchdog from the declared cadence')
    self.assertEqual((sent[1]['state'],sent[1]['name']),('ok','Klok'))
    self.assertEqual(sent[2]['x'],{'rise':'05:15','set':'17:50'},'fake HA has no time zone: UTC')
    m.ha.states['sensor.screen_firmware']={'state':'0.2.13'};m.ha.messages.clear()