feat(historian): #674 HistoryUpdate posture — future-skew bound, Primary gate, SqlServer v1 accepted, QuestDB TTL pin

- HistoryUpdate items with SourceTimestamp > now + ServerHistorian:HistoryUpdateMaxFutureSkew
  (default 1 day, <=0 disables) => BadOutOfRange in the node manager (every backend, never sent);
  clock injected via OtOpcUaNodeManager.Clock (host TimeProvider).
- HistoryUpdate is Primary-only: off-Primary => BadInvalidState per node, after authorization,
  same IDriverPrimaryRoleSource verdict as the native-ack gate; HistoryRead ungated.
- SqlServer: base schema requirement back to v1; SupportsModifiedTrail (v>=2). On v1 with
  AutoCreateSchema=false: writes/reads/events/retention work, modified reads + HistoryUpdate =>
  BadHistoryOperationUnsupported with nothing sent, retention skips SampleModified, one Warning per boot.
- QuestDB integration test pinning wall-clock TTL (far-future row evicts only partitions older
  than the TTL by the wall clock), with a positive control.
- Docs: Historian.md, Configuration.md, security.md, CLAUDE.md (incl. QuestDB retry duplicates,
  #674.4 anonymous-readable trail with ACL off, #674.5 not implemented).

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

docs/Configuration.md

@@ -410,7 +410,7 @@ Validated at host start (driver-role nodes) when `ServerHistorian:Enabled` **or*
 | `ServerHistorian:SqlServer:ConnectionString` | `""` | **Required.** Historian database connection string (not the ConfigDb). Supply via `${secret:OT-HISTORIAN-SQL}` or env `ServerHistorian__SqlServer__ConnectionString`; the database must already exist. |
 | `ServerHistorian:SqlServer:Schema` | `hist` | Must match `^[A-Za-z_][A-Za-z0-9_]{0,127}$` (spliced into DDL/DML). |
 | `ServerHistorian:SqlServer:CommandTimeout` | `00:00:30` | Must be `> 0`; rounded up to whole seconds. |
-| `ServerHistorian:SqlServer:AutoCreateSchema` | `true` | `true` applies the embedded schema script under an app-lock on first use; `false` only verifies `SchemaVersion >= 1` and fails every historian call (health `LastError`, no crash) if behind. |
+| `ServerHistorian:SqlServer:AutoCreateSchema` | `true` | `true` applies the embedded schema scripts under an app-lock on first use (upgrading a v1 schema to v2); `false` only verifies `SchemaVersion >= 1` and fails every historian call (health `LastError`, no crash) if behind. A verified **v1** schema (no `002_sample_modified.sql`) is served with modified-value reads and HistoryUpdate refused `BadHistoryOperationUnsupported`, retention skipping `SampleModified`, and one Warning per boot (#674). |
 | `ServerHistorian:SqlServer:RetentionDays` | unset | Days of history kept (source time), `>= 1` when set; unset keeps everything. Enables the Primary-gated purge of `hist.Sample`/`hist.Event` (see [Historian.md](Historian.md#retention-retentiondays)). |
 | `ServerHistorian:SqlServer:PurgeInterval` | `01:00:00` | Purge cadence; must be `> 0`. |
 | `ServerHistorian:SqlServer:PurgeBatchSize` | `4000` | Rows per `DELETE TOP (n)` batch; `>= 1`. Keep under ~5000 to avoid lock escalation. |
@@ -430,7 +430,12 @@ when `ServerHistorian:Enabled` **or** `AlarmHistorian:Enabled` is true (`QuestDb
 | `ServerHistorian:QuestDb:VisibilityTimeout` | `00:00:05` | Must be `>= 0`. How long a write waits for its rows to become visible to queries (WAL apply); `0` disables the wait. A timeout only logs a Warning. |
 
 HistoryUpdate (SqlServer and QuestDb only; QuestDb deletes are soft — tombstones) additionally needs `ServerHistorian:Enabled=true` and a key
-whose principal holds the `HistoryUpdate` permission — see [`docs/security.md`](security.md#historyupdate-historian-writes). Full semantics,
+whose principal holds the `HistoryUpdate` permission — see [`docs/security.md`](security.md#historyupdate-historian-writes). It is served
+only on the redundancy **Primary** (`BadInvalidState` elsewhere, #674) and is bounded by one backend-independent key:
+
+| Key | Default | Meaning |
+|---|---|---|
+| `ServerHistorian:HistoryUpdateMaxFutureSkew` | `1.00:00:00` (1 day) | TimeSpan. A HistoryUpdate (Insert / Replace / Update) item whose `SourceTimestamp` is later than server-clock now + this is refused `BadOutOfRange` before any backend sees it (#674 — a far-future typo could otherwise age out a QuestDB TTL table or poison the history). Applies to every backend; the live recorder is not bounded. Non-positive disables the bound. | Full semantics,
 schema, aggregates and the docker-dev recipe: [`docs/Historian.md`](Historian.md#sql-server-backend) (SqlServer) and
 [`docs/Historian.md`](Historian.md#questdb-backend) (QuestDb: the µs timestamp rules, pre-1970 limits, TTL and the docker-dev overlay).