fix: address pre-release review findings (2026-06-23)

Hardening from the pre-release review of the 06-19/06-23 roadmap batches:
solar timezone crash, webhook header CRLF, MQTT topic-prefix injection,
get_stats thread-safe copy, MQTT discovery lock, reactive_mode Literal,
and calibration modal accessibility. Adds regression coverage in
test_release_review_2026_06_23.py.

server/tests/core/test_automation_rule_handlers.py

@@ -19,6 +19,7 @@ from ledgrab.storage.automation import (
     DisplayStateRule,
     HomeAssistantRule,
     HTTPPollRule,
+    ManualTriggerRule,
     MQTTRule,
     Rule,
     SolarRule,
@@ -30,6 +31,7 @@ from ledgrab.storage.automation import (
 
 EXPECTED_RULE_TYPES = {
     StartupRule,
+    ManualTriggerRule,
     ApplicationRule,
     TimeOfDayRule,
     SolarRule,