refactor: DB schema fixes + container renames + compose include + audit sprint

- FindingsLedger: change schema from public to findings (V3-01)
- Add 9 migration module plugins: RiskEngine, Replay, ExportCenter, Integrations, Signer, IssuerDirectory, Workflow, PacksRegistry, OpsMemory (V4-01 to V4-09)
- Remove 16 redundant inline CREATE SCHEMA patterns (V4-10)
- Rename export→export-web, excititor→excititor-web for consistency
- Compose stella-ops.yml: thin wrapper using include: directive
- Fix dead /api/v1/jobengine/* gateway routes → release-orchestrator/packsregistry
- Scheduler plugin architecture: ISchedulerJobPlugin + ScanJobPlugin + DoctorJobPlugin
- Create unified audit sink sprint plan
- VulnExplorer integration tests + gap analysis

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

src/Findings/StellaOps.Findings.Ledger/Infrastructure/Postgres/FindingsLedgerDbContextFactory.cs

@@ -7,7 +7,7 @@ namespace StellaOps.Findings.Ledger.Infrastructure.Postgres;
 
 internal static class FindingsLedgerDbContextFactory
 {
-    public const string DefaultSchemaName = "public";
+    public const string DefaultSchemaName = "findings";
 
     public static FindingsLedgerDbContext Create(NpgsqlConnection connection, int commandTimeoutSeconds, string schemaName)
     {