feat: Implement provisioning pipelines for subscription management

- Add ReactivatePipeline to handle subscription reactivation, including scaling Docker services, health verification, status updates, audit logging, and broadcasting status changes.
- Introduce RotateCredentialsPipeline for OAuth2 credential rotation, managing the deletion of old apps, creation of new ones, credential storage, access verification, and audit logging.
- Create StepRunner to manage job step execution, including lifecycle management and progress broadcasting via SignalR.
- Implement SuspendPipeline for subscription suspension, scaling down services, updating statuses, logging audits, and broadcasting changes.
- Add UpdateScreenLimitPipeline to update Xibo CMS screen limits and record snapshots.
- Introduce XiboFeatureManifests for hardcoded feature ACLs per role.
- Add docker-compose.dev.yml for local development with PostgreSQL setup.

.env.example

@@ -0,0 +1,11 @@
+# OTSSignsOrchestrator.Server — required environment variables
+# Copy to .env and fill in real values.
+
+ConnectionStrings__OrchestratorDb=Host=localhost;Port=5432;Database=orchestrator_dev;Username=ots;Password=devpassword
+Stripe__WebhookSecret=whsec_...
+Stripe__SecretKey=sk_test_...
+Jwt__Key=change-me-to-a-random-256-bit-key
+Authentik__BaseUrl=https://auth.example.com
+Authentik__ApiToken=
+SendGrid__ApiKey=SG....
+OTS_SIGNS_SERVER_URL=http://localhost:5000