v2.26.0: fix SSE fanout crash and branded logo FOUC

- Fix SSE fanout thread AttributeError when source queue is None during
  interpreter shutdown by snapshotting to local variable with null guard
- Fix branded "i" logo rendering oversized on first page load (FOUC) by
  adding inline width/height to SVG elements across 10 templates
- Bump version to 2.26.0 in config.py, pyproject.toml, and CHANGELOG.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_bluetooth_aggregator.py

@@ -1,15 +1,17 @@
 """Unit tests for Bluetooth device aggregation."""
 
-import pytest
 from datetime import datetime, timedelta
-from unittest.mock import MagicMock, patch
+
+import pytest
 
 from utils.bluetooth.aggregator import DeviceAggregator
-from utils.bluetooth.models import BTObservation, BTDeviceAggregate
 from utils.bluetooth.constants import (
-    MAX_RSSI_SAMPLES,
     DEVICE_STALE_TIMEOUT as DEVICE_STALE_SECONDS,
 )
+from utils.bluetooth.constants import (
+    MAX_RSSI_SAMPLES,
+)
+from utils.bluetooth.models import BTObservation
 
 
 @pytest.fixture