feat: phase 6 production hardening + DB-to-DB transfer

Security:
- Graceful shutdown: http.Server + signal.NotifyContext, 10s drain,
  retention sweeper cancelled before pool close
- Scoped API keys (migration 00006): ingest/read/write/admin enforced in
  auth middleware; scope picker + badges in Settings UI; scopeless legacy
  keys act as admin. Read-only keys now get 403 on ingest (verified live)
- nginx: baseline security headers on all responses, CSP scoped to SPA;
  fixed add_header inheritance shadowing
- better-auth rate limit enabled unconditionally (was gated on NODE_ENV,
  which the shipped .env sets to development)
- Mailpit moved to docker-compose.dev.yml; prod compose cannot expose it
- setup.sh generates PRIMORA_ENCRYPTION_KEY

Reliability/ops:
- Retention: per-project retention_{events,audit,webhook}_days
  (migration 00007, 0=off) + hourly RetentionSweeper; edit UI in Projects
- GET /api/v1/metrics Prometheus exposition
- compose: healthchecks + restart policies everywhere, dragonfly pinned
  to v2.0.0, depends_on service_healthy
- backup.sh/restore.sh (pg_dump -Fc + storage volume); restore verified
  against scratch postgres+volume
- .dockerignore: exclude target dirs (build context was 4.7GB)

Correctness/testing:
- DBX transfer endpoint: POST /db-connections/:id/transfer — SQL or Redis
  target, 1000-row bound, server-side creds (verified live pg→dragonfly)
- Pagination audit: ListComponents capped at 500 (auto-registers)
- CI: goose up/reset/up job + compose e2e-smoke job (smoke-e2e.sh
  verified locally: signup, bootstrap, scoped keys, ingest, metrics)
- k6 load sanity script: 6650 reqs, ~217/s, 0 real failures, p95 221ms
  (429s = configured rate limiter working)

Docs: DEPLOYMENT_GUIDE.md, PRODUCTION_READINESS.md; verify script
repaired (stale refs + set -e arithmetic abort). ROADMAP: phase 2 +
phase 6 marked complete.

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/internal/database/db/querier.go

@@ -100,6 +100,15 @@ type Querier interface {
 	RemoveProjectMember(ctx context.Context, arg RemoveProjectMemberParams) (CoreProjectMember, error)
 	RemoveProjectMembershipsForOrganizationUser(ctx context.Context, arg RemoveProjectMembershipsForOrganizationUserParams) error
 	RevokeAPIKey(ctx context.Context, arg RevokeAPIKeyParams) (CoreApiKey, error)
+	SweepExpiredAuditLogs(ctx context.Context) (int64, error)
+	// Per-project retention sweeps. A retention of 0 days disables the sweep for
+	// that stream. Pending webhook deliveries are never swept — they may still be
+	// retrying.
+	SweepExpiredEvents(ctx context.Context) (int64, error)
+	// Org-scoped audit rows (project_id NULL) have no project retention — sweep
+	// them on a fixed 365-day floor so they cannot grow unbounded.
+	SweepExpiredOrgAuditLogs(ctx context.Context) (int64, error)
+	SweepExpiredWebhookDeliveries(ctx context.Context) (int64, error)
 	TouchAPIKey(ctx context.Context, id uuid.UUID) error
 	UpdateBucketByID(ctx context.Context, arg UpdateBucketByIDParams) (CoreBucket, error)
 	UpdateCollection(ctx context.Context, arg UpdateCollectionParams) (CoreCollection, error)