Add call graph fixtures for various languages and scenarios

- Introduced `all-edge-reasons.json` to test edge resolution reasons in .NET.
- Added `all-visibility-levels.json` to validate method visibility levels in .NET.
- Created `dotnet-aspnetcore-minimal.json` for a minimal ASP.NET Core application.
- Included `go-gin-api.json` for a Go Gin API application structure.
- Added `java-spring-boot.json` for the Spring PetClinic application in Java.
- Introduced `legacy-no-schema.json` for legacy application structure without schema.
- Created `node-express-api.json` for an Express.js API application structure.

src/Signals/__Tests/StellaOps.Signals.Tests/UnknownsDecayServiceTests.cs

@@ -475,6 +475,20 @@ public class UnknownsDecayServiceTests
             return Task.FromResult<IReadOnlyList<UnknownSymbolDocument>>(
                 _stored.Where(x => x.Band == band).Take(limit).ToList());
         }
+
+        public Task<IReadOnlyList<UnknownSymbolDocument>> QueryAsync(UnknownsBand? band, int limit, int offset, CancellationToken cancellationToken)
+        {
+            var query = _stored.AsEnumerable();
+            if (band.HasValue)
+                query = query.Where(x => x.Band == band.Value);
+            return Task.FromResult<IReadOnlyList<UnknownSymbolDocument>>(
+                query.Skip(offset).Take(limit).ToList());
+        }
+
+        public Task<UnknownSymbolDocument?> GetByIdAsync(string id, CancellationToken cancellationToken)
+        {
+            return Task.FromResult(_stored.FirstOrDefault(x => x.Id == id));
+        }
     }
 
     private sealed class InMemoryDeploymentRefsRepository : IDeploymentRefsRepository
@@ -492,6 +506,13 @@ public class UnknownsDecayServiceTests
         {
             return Task.FromResult<IReadOnlyList<string>>(Array.Empty<string>());
         }
+
+        public Task UpsertAsync(DeploymentRef deployment, CancellationToken cancellationToken) => Task.CompletedTask;
+
+        public Task BulkUpsertAsync(IEnumerable<DeploymentRef> deployments, CancellationToken cancellationToken) => Task.CompletedTask;
+
+        public Task<DeploymentSummary?> GetSummaryAsync(string purl, CancellationToken cancellationToken) =>
+            Task.FromResult<DeploymentSummary?>(null);
     }
 
     private sealed class InMemoryGraphMetricsRepository : IGraphMetricsRepository
@@ -508,6 +529,15 @@ public class UnknownsDecayServiceTests
             _metrics.TryGetValue($"{symbolId}:{callgraphId}", out var metrics);
             return Task.FromResult(metrics);
         }
+
+        public Task UpsertAsync(GraphMetrics metrics, CancellationToken cancellationToken) => Task.CompletedTask;
+
+        public Task BulkUpsertAsync(IEnumerable<GraphMetrics> metrics, CancellationToken cancellationToken) => Task.CompletedTask;
+
+        public Task<IReadOnlyList<string>> GetStaleCallgraphsAsync(TimeSpan maxAge, int limit, CancellationToken cancellationToken) =>
+            Task.FromResult<IReadOnlyList<string>>(Array.Empty<string>());
+
+        public Task DeleteByCallgraphAsync(string callgraphId, CancellationToken cancellationToken) => Task.CompletedTask;
     }
 
     #endregion