Phase 0 WP-0.2–0.9: Implement Commons (types, entities, interfaces, messages, protocol, tests)

- WP-0.2: Namespace/folder skeleton (26 directories)
- WP-0.3: Shared data types (6 enums, RetryPolicy, Result<T>)
- WP-0.4: 24 domain entity POCOs across 10 domain areas
- WP-0.5: 7 repository interfaces with full CRUD signatures
- WP-0.6: IAuditService cross-cutting interface
- WP-0.7: 26 message contract records across 8 concern areas
- WP-0.8: IDataConnection protocol abstraction with batch ops
- WP-0.9: 8 architectural constraint enforcement tests
All 40 tests pass, zero warnings.

src/ScadaLink.Commons/Interfaces/Repositories/ICentralUiRepository.cs

@@ -0,0 +1,19 @@
+using ScadaLink.Commons.Entities.Deployment;
+using ScadaLink.Commons.Entities.Instances;
+using ScadaLink.Commons.Entities.Sites;
+using ScadaLink.Commons.Entities.Templates;
+
+namespace ScadaLink.Commons.Interfaces.Repositories;
+
+public interface ICentralUiRepository
+{
+    Task<IReadOnlyList<Site>> GetAllSitesAsync(CancellationToken cancellationToken = default);
+    Task<IReadOnlyList<DataConnection>> GetDataConnectionsBySiteIdAsync(int siteId, CancellationToken cancellationToken = default);
+    Task<IReadOnlyList<SiteDataConnectionAssignment>> GetAllSiteDataConnectionAssignmentsAsync(CancellationToken cancellationToken = default);
+    Task<IReadOnlyList<Template>> GetTemplateTreeAsync(CancellationToken cancellationToken = default);
+    Task<IReadOnlyList<Instance>> GetInstancesFilteredAsync(int? siteId = null, int? templateId = null, string? searchTerm = null, CancellationToken cancellationToken = default);
+    Task<IReadOnlyList<DeploymentRecord>> GetRecentDeploymentsAsync(int count, CancellationToken cancellationToken = default);
+    Task<IReadOnlyList<Area>> GetAreaTreeBySiteIdAsync(int siteId, CancellationToken cancellationToken = default);
+
+    Task<int> SaveChangesAsync(CancellationToken cancellationToken = default);
+}