Remove DuckHog Flight ingress

[bill-ph]

What changed

• remove the external Arrow Flight SQL ingress and all DuckHog/port 8815 configuration, listeners, auth, metrics, and deployment exposure
• remove durable Flight reconnect records and worker-takeover paths that existed only for external Flight clients
• make performance and scenario tooling pgwire-only
• update manifests, dashboards, runbooks, admin UI copy, and local development guidance
• retain Arrow Flight SQL exclusively as the internal control-plane-to-worker transport on worker port 8816 or Unix sockets

Why

Duckgres control-plane clients should use one supported interface: PostgreSQL wire protocol. Keeping the DuckHog ingress duplicated authentication, session lifecycle, reconnect, observability, and deployment behavior without being part of the desired public surface.

Impact

• client-facing control-plane ports are now 5432 for pgwire and 9090 for metrics/admin API
• removed Flight CLI flags are rejected as unknown; deployment charts must remove any --flight-port and Flight TTL arguments in the same rollout
• existing config-store databases may retain an unused legacy Flight session table; this change stops creating or reading it and intentionally avoids a destructive schema migration
• internal worker RPC remains Arrow Flight SQL and is not affected

Checks

• just lint
• just test-unit
• just test-controlplane
• just test-controlplane-k8s
• just test-configstore-integration
• just test-perf
• just test-scenario

[github-actions]

Test Impact Plan

Deterministic summary of how this PR changes tests, CI runners, and coverage-risk signals.

Summary

Area	Added	Changed	Deleted
Test files	0	39	8
E2E/journey files	0	0	0
Workflow files	0	0	0

Signals

• Test cases: +10 / -99
• Assertions: +31 / -524
• Skips or known failures added: 0
• Workflow continue-on-error added: 0
• Workflow path filters added: 0
• Test commands removed from justfile: 0
• E2E/journey retry lines added: 0

Coverage risk: likely reduced

Warnings

• Test files deleted (likely reduced)
  • controlplane/flight_ingress_adapter_test.go
  • controlplane/flight_ingress_test.go
  • controlplane/org_reserved_pool_reconnect_test.go
  • server/flightsqlingress/ingress_test.go
  • server/flightsqlingress/user_secrets_test.go
  • tests/controlplane/flight_ingress_test.go
  • tests/perf/drivers/flight/driver.go
  • tests/perf/drivers/flight/driver_test.go
• Test cases removed (likely reduced)
  • 99 removed vs 10 added
• Assertions removed (needs review)
  • 524 removed vs 31 added
• Files without patch data (needs review)
  • controlplane/metrics_stub.go
  • controlplane/metrics_test.go