refactor(findings): merge VulnExplorer into Findings Ledger

- Move VulnExplorer DTOs into Ledger WebService Contracts/VulnExplorer/
  (VulnModels, VexDecisionModels, TriageWorkflowModels, AttestationModels,
   FixVerificationModels, EvidenceSubgraphContracts)
- Create VulnExplorerEndpoints.cs mounting all 10 original endpoints
  (/v1/vulns, /v1/vex-decisions, /v1/evidence-subgraph,
   /v1/fix-verifications, /v1/audit-bundles)
- Create adapter services (VulnExplorerAdapters.cs) that delegate to
  existing Ledger services (FindingSummaryService, VulnerabilityDetailService,
  EvidenceGraphBuilder, VexConsensusService)
- Wire VulnExplorer authorization policies and service registrations
  in Ledger Program.cs
- Comment out api (VulnExplorer) container in docker-compose.stella-ops.yml
- Add vulnexplorer.stella-ops.local as network alias on findings-ledger-web
- Update gateway route: /api/vuln-explorer(..) -> findings.stella-ops.local
- Update STELLAOPS_VULNEXPLORER_URL -> findings.stella-ops.local
- Comment out VulnExplorer in services-matrix.env and hosts file
- Update docs: port-registry, component-map, module-matrix, webservice-catalog,
  findings-ledger README
- Eliminates 1 container (stellaops-api)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/technical/architecture/webservice-catalog.md

@@ -5,7 +5,7 @@ This page is the source-of-truth inventory for Stella Ops `*.WebService` runtime
 ## Scope and contract
 - Inventory source: `rg --files src -g "*WebService.csproj"`.
 - Includes active runtime webservices only (31 services).
-- Excludes non-`WebService` API binaries (for example `StellaOps.Policy.Engine`, `StellaOps.Policy.Gateway`, `StellaOps.Graph.Api`, `StellaOps.VulnExplorer.Api`, `StellaOps.Symbols.Server`, `StellaOps.Registry.TokenService`, `StellaOps.SmRemote.Service`) even though they may bind `*.stella-ops.local` aliases.
+- Excludes non-`WebService` API binaries (for example `StellaOps.Policy.Engine`, `StellaOps.Policy.Gateway`, `StellaOps.Graph.Api`, `StellaOps.Symbols.Server`, `StellaOps.Registry.TokenService`, `StellaOps.SmRemote.Service`) even though they may bind `*.stella-ops.local` aliases. Note: `StellaOps.VulnExplorer.Api` has been merged into `StellaOps.Findings.Ledger.WebService` (SPRINT_20260408_002).
 - Canonical runtime hostname form: `<service>.stella-ops.local`.
 
 ## Runtime hostname convention and exceptions