refactor(sf,site): both stores take ILocalDb instead of a connection string

Tasks 5 and 6 of the Phase 2 plan, committed together because their test
fallout is entangled — several fixtures construct both stores.

StoreAndForwardStorage and SiteStorageService now take ILocalDb. Connections
come from ILocalDb.CreateConnection(), which hands out an already-open,
pragma-configured connection carrying the zb_hlc_next() UDF the capture triggers
call; a raw connection would lack the UDF and every write to a replicated table
would fail closed. Deleted with the connection strings: S&F's
EnsureDatabaseDirectoryExists and its per-open busy_timeout pragma, and the site
service's BusyTimeoutFloorSeconds normalization — LocalDb owns all of it now.

DI: AddSiteRuntime's string overload is gone (nothing left to supply), so the
Host calls the no-arg form. ScadaBridge:Database:SiteDbPath and
StoreAndForwardOptions.SqliteDbPath survive only as the migrator's source
locations in Tasks 8/9.

Two things the plan did not anticipate, both worth reading:

1. FOUND A REAL LATENT DEFECT, from Phase 1, now fixed. The plan assumed
   directory creation simply moved to LocalDb along with file ownership. It did
   not: the LocalDb library never creates the parent directory, and
   SqliteLocalDb opens the file eagerly in its constructor — so a missing
   directory is a hard boot failure ("SQLite Error 14: unable to open database
   file"), not a degraded start. The default site config points at the RELATIVE
   path ./data/site-localdb.db, so any site node without a pre-existing data/
   directory fails to boot. The docker rig escapes only because its volume mount
   happens to create /app/data — a coincidence that would have hidden this until
   a bare-metal or fresh deployment. This has been latent since Phase 1 made
   LocalDb:Path required; deleting S&F's EnsureDatabaseDirectoryExists here
   would have widened it. Re-established the guarantee at the layer that now
   owns the path (SiteLocalDbDirectory.Ensure, called before AddZbLocalDb) and
   pinned it with SiteLocalDbDirectoryTests. Non-vacuity is not assumed: two
   tests written against the wrong assumption failed with exactly this
   SQLite Error 14 before the fix existed.

2. Test fallout was ~7x the plan's estimate. The plan named "fixtures" in one
   project; the constructor change actually reaches 40 files across 7 test
   projects, and most used Mode=Memory;Cache=Shared — which LocalDb has no
   equivalent for, so every one had to move to a real temp file. Rather than
   copy the Phase 1 TestLocalDb fixture into 7 projects, added a shared
   tests/ZB.MOM.WW.ScadaBridge.TestSupport library (not a test project) so the
   WAL-sidecar cleanup and the "real, not stubbed" rationale live in one place.

Retargeted rather than deleted, in both directions: the S&F WAL test now asserts
against the LocalDb-backed store (WAL genuinely is LocalDb's job), while the
directory-creation test moved to Host.Tests (that guarantee is NOT LocalDb's).
SiteStorageServiceTests.Initialize_EnablesWalJournalMode got the same treatment.
DeploymentManagerMediumFindingsTests induced a persistence failure via an
unopenable path, which no longer reaches the assertion since the fixture now
throws first; it induces the same failure shape via an uninitialized store.

Verified: full solution build 0 warnings; SiteRuntime 532, Host 318,
AuditLog 355, ExternalSystemGateway 142, HealthMonitoring 97,
StoreAndForward 153 — 1597 passed, 0 failed.

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

tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Persistence/SiteStorageServiceTests.cs

@@ -1,7 +1,7 @@
-using Microsoft.Data.Sqlite;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime.Persistence;
+using ZB.MOM.WW.ScadaBridge.TestSupport;
 
 namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.Persistence;
 
@@ -9,20 +9,26 @@ namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.Persistence;
 /// Tests for SiteStorageService using file-based SQLite (temp files).
 /// Validates the schema, CRUD operations, and constraint behavior.
 /// </summary>
+/// <remarks>
+/// The service now takes an <c>ILocalDb</c> rather than a connection string, so the fixture
+/// is a real temp-file LocalDb. It stays a file (never in-memory): LocalDb has no in-memory
+/// mode, and the connections it hands out carry the pragmas and the <c>zb_hlc_next()</c> UDF
+/// the site tables' capture triggers depend on.
+/// </remarks>
 public class SiteStorageServiceTests : IAsyncLifetime, IDisposable
 {
-    private readonly string _dbFile;
+    private readonly TestLocalDb _localDb;
     private SiteStorageService _storage = null!;
 
     public SiteStorageServiceTests()
     {
-        _dbFile = Path.Combine(Path.GetTempPath(), $"site-storage-test-{Guid.NewGuid():N}.db");
+        _localDb = TestLocalDb.CreateTemp("site-storage-test");
     }
 
     public async Task InitializeAsync()
     {
         _storage = new SiteStorageService(
-            $"Data Source={_dbFile}",
+            _localDb.Db,
             NullLogger<SiteStorageService>.Instance);
         await _storage.InitializeAsync();
     }
@@ -31,7 +37,11 @@ public class SiteStorageServiceTests : IAsyncLifetime, IDisposable
 
     public void Dispose()
     {
-        try { File.Delete(_dbFile); } catch { /* cleanup */ }
+        // Dispose first — the master connection anchors the WAL, so the sidecars
+        // cannot be removed while it is open.
+        var path = _localDb.Path;
+        _localDb.Dispose();
+        TestLocalDb.DeleteFiles(path);
     }
 
     [Fact]
@@ -45,10 +55,17 @@ public class SiteStorageServiceTests : IAsyncLifetime, IDisposable
     [Fact]
     public async Task Initialize_EnablesWalJournalMode()
     {
-        // WAL is set once at InitializeAsync (persistent, database-level). A file-backed DB
-        // is required — WAL is not available for :memory: databases.
-        await using var conn = _storage.CreateConnection();
-        await conn.OpenAsync();
+        // ── Invariant that moved owner ──
+        // WAL used to be SiteStorageService's own job (an explicit PRAGMA in
+        // InitializeAsync). LocalDb now owns the file and its pragmas, so the service no
+        // longer sets it. The guarantee production depends on has NOT moved: without WAL
+        // the site's concurrent readers and writers start serializing on "database is
+        // locked". So rather than deleting this test with the code that used to provide
+        // the pragma, it is retargeted to assert the same guarantee against the new,
+        // LocalDb-backed service. journal_mode is persistent and file-scoped, so any
+        // connection observes it. A file-backed DB is still required — WAL is not
+        // available for :memory: databases, which is also why LocalDb has no in-memory mode.
+        await using var conn = _storage.CreateConnection(); // already open — do NOT call OpenAsync
         await using var cmd = conn.CreateCommand();
         cmd.CommandText = "PRAGMA journal_mode;";
         var mode = (string)(await cmd.ExecuteScalarAsync())!;
@@ -219,8 +236,10 @@ public class SiteStorageServiceTests : IAsyncLifetime, IDisposable
         string instanceName, string configJson, string deploymentId,
         string revisionHash, bool isEnabled, DateTimeOffset deployedAt)
     {
-        await using var conn = new SqliteConnection($"Data Source={_dbFile}");
-        await conn.OpenAsync();
+        // Seeded through the service's own (already-open) LocalDb connection: a raw
+        // SqliteConnection would lack the pragmas and the zb_hlc_next() UDF the site
+        // tables' capture triggers call.
+        await using var conn = _storage.CreateConnection();
         await using var cmd = conn.CreateCommand();
         cmd.CommandText = @"
             INSERT INTO deployed_configurations