docs+chore(localdb): phase-2 rig config + docs

Enables the alarm store-and-forward sink on all four driver nodes of the
docker-dev rig -- the replicating site-a pair and the default-OFF site-b pin
-- so the live gate has a real buffer to watch converge, and can see that
site-b's sink works as a plain node-local queue with no peer traffic.

Two rig details worth stating rather than rediscovering. The endpoint is
deliberately unresolvable: there is no HistorianGateway here, so every drain
attempt fails, which is exactly the historian-outage state the buffer exists
for. But it still has to be a syntactically valid absolute http(s) URI or the
host refuses to start, because ServerHistorianOptionsValidator is
consumer-gated -- AlarmHistorian:Enabled=true makes the endpoint required
even while ServerHistorian:Enabled=false. And MaxAttempts is raised far above
the production default of 10, which against a permanently unreachable gateway
would dead-letter the entire queue about five minutes in, turning a buffering
test into a dead-letter test.

Docs record what an operator now has to know: that a rising queue depth on a
Secondary is correct and on BOTH nodes is not (that shape is a redundancy
snapshot naming neither node -- check node identity before suspecting the
sink), that delivery is at-least-once across a failover by design with no
dedup layer, and that AlarmHistorian:DatabasePath is removed but should be
left in place through the upgrade because the migrator still reads it to find
the file to copy.

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

docs/README.md

@@ -30,7 +30,7 @@ The project was originally called **LmxOpcUa** (a single-driver Galaxy/MXAccess
 | [Subscriptions.md](v1/Subscriptions.md) | Monitored items → `ISubscribable` + per-driver subscription refcount (v1 archive) |
 | [AlarmTracking.md](AlarmTracking.md) | `IAlarmSource` + `AlarmSurfaceInvoker` + OPC UA alarm conditions — native Galaxy alarms end-to-end (live) |
 | [AlarmTracking.md](v1/AlarmTracking.md) | Original alarm-tracking write-up (v1 archive) |
-| [AlarmHistorian.md](AlarmHistorian.md) | `Core.AlarmHistorian` store-and-forward SQLite sink — `SqliteStoreAndForwardSink`, `IAlarmHistorianWriter`, dead-letter/retry/eviction |
+| [AlarmHistorian.md](AlarmHistorian.md) | `Core.AlarmHistorian` store-and-forward sink — `LocalDbStoreAndForwardSink`, the replicated `alarm_sf_events` buffer + Primary-only drain, `IAlarmHistorianWriter`, dead-letter/retry/eviction |
 | [DataTypeMapping.md](v1/DataTypeMapping.md) | Per-driver `DriverAttributeInfo` → OPC UA variable types (v1 archive — live mapping is in `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/Browse/DataTypeMap.cs`) |
 | [IncrementalSync.md](IncrementalSync.md) | Address-space rebuild on redeploy + `sp_ComputeGenerationDiff` |
 | [HistoricalDataAccess.md](v1/HistoricalDataAccess.md) | `IHistoryProvider` as a per-driver optional capability (v1 archive) |