Phase 3B: Site I/O & Observability — Communication, DCL, Script/Alarm actors, Health, Event Logging

Communication Layer (WP-1–5):
- 8 message patterns with correlation IDs, per-pattern timeouts
- Central/Site communication actors, transport heartbeat config
- Connection failure handling (no central buffering, debug streams killed)

Data Connection Layer (WP-6–14, WP-34):
- Connection actor with Become/Stash lifecycle (Connecting/Connected/Reconnecting)
- OPC UA + LmxProxy adapters behind IDataConnection
- Auto-reconnect, bad quality propagation, transparent re-subscribe
- Write-back, tag path resolution with retry, health reporting
- Protocol extensibility via DataConnectionFactory

Site Runtime (WP-15–25, WP-32–33):
- ScriptActor/ScriptExecutionActor (triggers, concurrent execution, blocking I/O dispatcher)
- AlarmActor/AlarmExecutionActor (ValueMatch/RangeViolation/RateOfChange, in-memory state)
- SharedScriptLibrary (inline execution), ScriptRuntimeContext (API)
- ScriptCompilationService (Roslyn, forbidden API enforcement, execution timeout)
- Recursion limit (default 10), call direction enforcement
- SiteStreamManager (per-subscriber bounded buffers, fire-and-forget)
- Debug view backend (snapshot + stream), concurrency serialization
- Local artifact storage (4 SQLite tables)

Health Monitoring (WP-26–28):
- SiteHealthCollector (thread-safe counters, connection state)
- HealthReportSender (30s interval, monotonic sequence numbers)
- CentralHealthAggregator (offline detection 60s, online recovery)

Site Event Logging (WP-29–31):
- SiteEventLogger (SQLite, 6 event categories, ISO 8601 UTC)
- EventLogPurgeService (30-day retention, 1GB cap)
- EventLogQueryService (filters, keyword search, keyset pagination)

541 tests pass, zero warnings.

src/ScadaLink.SiteEventLogging/ScadaLink.SiteEventLogging.csproj

@@ -8,7 +8,10 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.Data.Sqlite" Version="10.0.5" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.5" />
+    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="10.0.5" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.5" />
     <PackageReference Include="Microsoft.Extensions.Options" Version="10.0.5" />
   </ItemGroup>
 
@@ -16,4 +19,8 @@
     <ProjectReference Include="../ScadaLink.Commons/ScadaLink.Commons.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <InternalsVisibleTo Include="ScadaLink.SiteEventLogging.Tests" />
+  </ItemGroup>
+
 </Project>