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.Host.Tests/SiteLocalDbDirectoryTests.cs

@@ -0,0 +1,70 @@
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using ZB.MOM.WW.LocalDb;
+
+namespace ZB.MOM.WW.ScadaBridge.Host.Tests;
+
+/// <summary>
+/// Pins that a site node creates the directory holding <c>LocalDb:Path</c> before the
+/// database is opened.
+/// </summary>
+/// <remarks>
+/// <para>
+/// This guarantee used to live in <c>StoreAndForwardStorage.EnsureDatabaseDirectoryExists</c>,
+/// which created the parent directory for its own SQLite file. LocalDb Phase 2 moved that
+/// file into the consolidated database — but the LocalDb library does <b>not</b> create the
+/// directory, and <c>SqliteLocalDb</c> opens the file eagerly in its constructor, so a
+/// missing directory is a hard boot failure ("SQLite Error 14: unable to open database
+/// file") rather than a degraded start.
+/// </para>
+/// <para>
+/// This is not hypothetical: the default site configuration points at the <i>relative</i>
+/// path <c>./data/site-localdb.db</c>, so any site node whose working directory has no
+/// <c>data/</c> subdirectory hits it. The docker rig escapes only because its volume mount
+/// creates <c>/app/data</c> — which is exactly the kind of coincidence that hides a defect
+/// until a bare-metal or fresh deployment.
+/// </para>
+/// </remarks>
+public class SiteLocalDbDirectoryTests
+{
+    [Fact]
+    public void SiteRegistration_CreatesTheLocalDbDirectory_WhenItDoesNotExist()
+    {
+        var root = Path.Combine(Path.GetTempPath(), "localdb-dir-test-" + Guid.NewGuid().ToString("N"));
+        var dbPath = Path.Combine(root, "nested", "site-localdb.db");
+        Assert.False(Directory.Exists(root));
+
+        try
+        {
+            var config = new ConfigurationBuilder()
+                .AddInMemoryCollection(new Dictionary<string, string?>
+                {
+                    ["LocalDb:Path"] = dbPath,
+                })
+                .Build();
+
+            // The registration path under test. Resolving ILocalDb is what actually opens
+            // the file, so this fails with SQLite Error 14 if the directory step regresses.
+            var services = new ServiceCollection();
+            SiteLocalDbDirectory.Ensure(config);
+            services.AddZbLocalDb(config);
+
+            using var provider = services.BuildServiceProvider();
+            using var scope = provider.CreateScope();
+            var db = scope.ServiceProvider.GetRequiredService<ILocalDb>();
+
+            Assert.NotNull(db);
+            Assert.True(Directory.Exists(Path.GetDirectoryName(dbPath)!));
+            Assert.True(File.Exists(dbPath));
+        }
+        finally
+        {
+            SqliteConnectionPoolCleanup();
+            if (Directory.Exists(root))
+                Directory.Delete(root, recursive: true);
+        }
+    }
+
+    private static void SqliteConnectionPoolCleanup() =>
+        Microsoft.Data.Sqlite.SqliteConnection.ClearAllPools();
+}