perf: close Theme 6 — 11 allocation / N+1 / lock-contention findings

Well-localised perf fixes across 8 modules.

Lock decoupling / SQL streaming:
- AuditLog-005: SqliteAuditWriter gains dedicated read-only _readConnection
  (+ _readLock) backed by WAL journal mode. GetBacklogStatsAsync,
  ReadPendingAsync, ReadPendingSinceAsync, ReadForwardedAsync no longer
  contend with the hot-path INSERT lock — backlog probes on a 30s timer
  can't stall the writer under multi-hundred-K Pending backlog.
- SEL-022: dropped Cache=Shared from SiteEventLogger's default connection
  string (single-connection logger; mode was dormant config).

Memory / streaming:
- CLI-019: bundle export streams base64 in 1 MB-aligned chunks via
  Convert.TryFromBase64Chars straight into the FileStream — no more
  full-bundle byte[] allocation.
- CentralUI-031: TransportImport now stages the upload to a per-session
  temp file under Path.GetTempPath() (replaces in-memory byte[] field);
  page implements IDisposable to delete the temp file on reset / new
  upload / dispose. Per-circuit working set drops from ~100 MB to ~80 KB.

N+1 hoisting:
- Transport-008: added ITemplateEngineRepository.GetTemplatesWithChildrenAsync
  bulk method; BundleImporter.PreviewAsync calls it once instead of per-
  template-name. Single query with .Include(...).AsSplitQuery().
- DM-023: BuildDeployArtifactsCommandAsync's per-site loop now references
  a pre-fetched GlobalArtifactSnapshot (shared scripts, external systems,
  DB connections, notification lists, SMTP) instead of re-querying per site.
- MgmtSvc-023: HandleQueryDeployments unfiltered branch uses one
  GetAllInstancesAsync bulk load + Dictionary<int,int?> lookup (was a
  GetInstanceByIdAsync per record).

Small allocations / per-tick rebuilds:
- InboundAPI-019: AuditWriteMiddleware gates EnableBuffering() on
  RequestHasBody() so GET/HEAD/DELETE/TRACE/OPTIONS and Content-Length:0
  requests skip the FileBufferingReadStream allocation.
- NotifOutbox-006: ResolveAdapters dictionary now cached on
  _adaptersCache (built lazily on first sweep) + actor-lifetime
  _adaptersScope; ResolveAdapters no longer rebuilds per dispatch tick.

Verify-only:
- Comm-017: Confirmed _inProgressDeployments was deleted by Comm-016 in
  commit ac96b83 — marked Resolved with that attribution. No code change.

Doc-correction:
- NS-022: Updated MailKitSmtpClientWrapper XML doc to spell out single-
  connection / per-delivery-factory contract (option (b) — transient
  client per Send — rejected because it re-handshakes TLS per email).

10+ new regression tests across 8 test projects. Build clean; affected
suites all green. README regenerated: 54 open (was 65).

src/ScadaLink.ConfigurationDatabase/Repositories/TemplateEngineRepository.cs

@@ -39,6 +39,30 @@ public class TemplateEngineRepository : ITemplateEngineRepository
         return await GetTemplateByIdAsync(id, cancellationToken);
     }
 
+    /// <inheritdoc />
+    public async Task<IReadOnlyList<Template>> GetTemplatesWithChildrenAsync(
+        IEnumerable<string> names, CancellationToken cancellationToken = default)
+    {
+        // Transport-008: bulk lookup replaces the per-name N+1 in
+        // BundleImporter.PreviewAsync. Filter out null / empty / duplicate
+        // names before the query so EF emits a clean, deduplicated IN clause.
+        if (names is null) return Array.Empty<Template>();
+        var distinct = names
+            .Where(n => !string.IsNullOrEmpty(n))
+            .Distinct(StringComparer.Ordinal)
+            .ToArray();
+        if (distinct.Length == 0) return Array.Empty<Template>();
+
+        return await _context.Templates
+            .Where(t => distinct.Contains(t.Name))
+            .Include(t => t.Attributes)
+            .Include(t => t.Alarms)
+            .Include(t => t.Scripts)
+            .Include(t => t.Compositions)
+            .AsSplitQuery()
+            .ToListAsync(cancellationToken);
+    }
+
     /// <inheritdoc />
     public async Task<IReadOnlyList<Template>> GetAllTemplatesAsync(CancellationToken cancellationToken = default)
     {