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

src/ZB.MOM.WW.ScadaBridge.StoreAndForward/ServiceCollectionExtensions.cs

@@ -1,6 +1,7 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
+using ZB.MOM.WW.LocalDb;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
 using ZB.MOM.WW.ScadaBridge.SiteEventLogging;
 
@@ -15,14 +16,12 @@ public static class ServiceCollectionExtensions
     /// <returns>The same <paramref name="services"/> collection, for chaining.</returns>
     public static IServiceCollection AddStoreAndForward(this IServiceCollection services)
     {
-        services.AddSingleton<StoreAndForwardStorage>(sp =>
-        {
-            var options = sp.GetRequiredService<IOptions<StoreAndForwardOptions>>().Value;
-            var logger = sp.GetRequiredService<ILogger<StoreAndForwardStorage>>();
-            return new StoreAndForwardStorage(
-                $"Data Source={options.SqliteDbPath}",
-                logger);
-        });
+        // The buffer now lives in the consolidated LocalDb database at LocalDb:Path, not
+        // at StoreAndForwardOptions.SqliteDbPath — that option survives only as the
+        // migrator's source location (Task 8).
+        services.AddSingleton<StoreAndForwardStorage>(sp => new StoreAndForwardStorage(
+            sp.GetRequiredService<ILocalDb>(),
+            sp.GetRequiredService<ILogger<StoreAndForwardStorage>>()));
 
         services.AddSingleton<StoreAndForwardService>(sp =>
         {