M3: live ingestion (MQTT/Tasmota + Home Assistant)

- PayloadExtractor: dot-path value/time extraction (Tasmota ENERGY.Total, bare scalars).
- MqttTopicMatcher: standard +/# wildcard matching.
- IngestionService: scale/offset, idempotent upsert on (meter_id, time), and a spurious-
  decrease guard for monotonic registers (allowed only with a reset/swap event) + source
  last-seen status.
- MqttMessageRouter + MqttIngestionWorker (MQTTnet 5): per-endpoint persistent connections,
  topic subscription, graceful degradation; secrets resolved by env-var reference.
- Home Assistant: HaStateClient (REST /api/states parse) + HomeAssistantWorker polling on
  each source's interval. HA-via-MQTT also works through the MQTT path.
- Ingestion workers gated by MeterVault:EnableLiveIngestion (off in tests).

85 tests green (53 Core + 32 integration): Tasmota payload → reading verified end to end.

Follow-up (polish): HA WebSocket push (state_changed) as an alternative to REST poll;
source-topic index caching in the router.

Claude-Session: https://claude.ai/code/session_01WujdMtMJPbxDpDnMeK22rr

src/Infrastructure/Options/MeterVaultOptions.cs

@@ -19,6 +19,9 @@ public sealed class MeterVaultOptions
     /// <summary>Run EF migrations on startup. Disable for tests that migrate out-of-band.</summary>
     public bool RunMigrationsAtStartup { get; set; } = true;
 
+    /// <summary>Start the MQTT/Home Assistant ingestion workers. Disable for tests.</summary>
+    public bool EnableLiveIngestion { get; set; } = true;
+
     /// <summary>How long full-resolution raw readings are retained (SDD §5.5, default 3 years).</summary>
     public int RawRetentionDays { get; set; } = 1095;
 }