Add integration tests for Proof Chain and Reachability workflows

- Implement ProofChainTestFixture for PostgreSQL-backed integration tests.
- Create StellaOps.Integration.ProofChain project with necessary dependencies.
- Add ReachabilityIntegrationTests to validate call graph extraction and reachability analysis.
- Introduce ReachabilityTestFixture for managing corpus and fixture paths.
- Establish StellaOps.Integration.Reachability project with required references.
- Develop UnknownsWorkflowTests to cover the unknowns lifecycle: detection, ranking, escalation, and resolution.
- Create StellaOps.Integration.Unknowns project with dependencies for unknowns workflow.

src/Scanner/StellaOps.Scanner.WebService/Program.cs

@@ -491,11 +491,10 @@ app.UseExceptionHandler(errorApp =>
     });
 });
 
-if (authorityConfigured)
-{
-    app.UseAuthentication();
-    app.UseAuthorization();
-}
+// Always add authentication and authorization middleware
+// Even in anonymous mode, endpoints use RequireAuthorization() which needs the middleware
+app.UseAuthentication();
+app.UseAuthorization();
 
 // Idempotency middleware (Sprint: SPRINT_3500_0002_0003)
 app.UseIdempotency();