feat(espnow): broadcast delivery with group-filtered routing

Send presets and select on broadcast with groups; unicast only for
per-device settings. V1 select as [preset_id, step?]. Sequence steps
use beat counts; manual presets get select each beat, auto only on
step change. Bridge downlink router, Pi envelope delivery, and tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_endpoints_pytest.py

@@ -676,13 +676,13 @@ def test_groups_sequences_scenes_palettes_patterns_endpoints(server):
     assert "presets" in first and "select" in first
     assert first["presets"]["__identify"]["p"] == "blink"
     assert first["presets"]["__identify"]["d"] == 50
-    assert first["select"]["pytest-dev"] == ["__identify"]
+    assert first["select"] == ["__identify"]
     deadline = time.monotonic() + 2.0
     while len(sender.sent) < 2 and time.monotonic() < deadline:
         time.sleep(0.02)
     assert len(sender.sent) >= 2
     second = json.loads(sender.sent[1][0])
-    assert second.get("select") == {"pytest-dev": ["off"]}
+    assert second.get("select") == ["off"]
 
     resp = c.post(
         f"{base_url}/devices",