feat(localdb): rewire SiteEventLogger onto the consolidated site database

Completes Task 5a of the LocalDb Phase 1 adoption plan. The GUID-id half landed
with Task 2 (727fa48c) because leaving it out would have committed a writer that
could not satisfy site_events.id NOT NULL; this is the connection half, which
was blocked on Task 3.

SiteEventLogger owned a SqliteConnection built from SiteEventLogOptions
.DatabasePath. It now takes ILocalDb and gets that connection from
CreateConnection() - already open, pragma-configured, and carrying the
zb_hlc_next() UDF that site_events' capture triggers call. It still owns and
disposes the connection; WithConnection's signature and locking semantics are
untouched, so EventLogQueryService and EventLogPurgeService are unaffected.

The connectionStringOverride seam is deleted rather than preserved. site_events
is a replicated table, so a raw connection lacks the UDF and fails closed on
every insert - an override could only produce a logger that cannot write. It had
no callers outside this class (the connectionStringOverride hits elsewhere in the
tree belong to SqliteAuditWriter, a different type).

Tests: a shared TestLocalDb helper gives each fixture a real ILocalDb over a temp
file. Real rather than stubbed on purpose - a stub handing back a bare
SqliteConnection would pass today and fail closed the moment the table is
registered, which is exactly the silent-wiring failure mode this family has hit
three times. ServiceWiringTests' DI path also needed AddZbLocalDb, mirroring
SiteServiceRegistration.

Verified: build 0 warnings; SiteEventLogging 70/70, Host 294/294,
SiteRuntime 530/530.

Claude-Session: https://claude.ai/code/session_01BL2Vu1ESDQ9SCN4gVKkdts

tests/ZB.MOM.WW.ScadaBridge.SiteEventLogging.Tests/EventLogPurgeServiceTests.cs

@@ -6,6 +6,7 @@ namespace ZB.MOM.WW.ScadaBridge.SiteEventLogging.Tests;
 public class EventLogPurgeServiceTests : IDisposable
 {
     private readonly SiteEventLogger _eventLogger;
+    private readonly TestLocalDb _localDb;
     private readonly string _dbPath;
     private readonly SiteEventLogOptions _options;
 
@@ -27,15 +28,19 @@ public class EventLogPurgeServiceTests : IDisposable
             RetentionDays = 30,
             MaxStorageMb = 1024
         };
+        _localDb = TestLocalDb.Create(_dbPath);
         _eventLogger = new SiteEventLogger(
             Options.Create(_options),
-            NullLogger<SiteEventLogger>.Instance);
+            NullLogger<SiteEventLogger>.Instance,
+            _localDb.Db);
     }
 
     public void Dispose()
     {
         _eventLogger.Dispose();
-        if (File.Exists(_dbPath)) File.Delete(_dbPath);
+        _localDb.Dispose();
+        TestLocalDb.DeleteFiles(_dbPath);
+        GC.SuppressFinalize(this);
     }
 
     private EventLogPurgeService CreatePurgeService(