Refactored to maintain a separate cloud version

Moves 12 packages from internal/ to pkg/ (config, id, validate, events, db,
auth, lifecycle, scheduler, channels, audit, service) so they can be imported
by the enterprise repo as a Go module dependency.

Introduces pkg/cpextension (shared Extension interface + ServerContext) and
pkg/cpserver (Run() entrypoint with functional options) so the enterprise
main.go can call cpserver.Run(cpserver.WithExtensions(...)) without duplicating
the 20-step server bootstrap. Adds db/migrations/embed.go for go:embed access
to OSS SQL migrations from the enterprise module.

cmd/control-plane/main.go is reduced to a 10-line wrapper around cpserver.Run.

pkg/channels/publisher.go

@@ -0,0 +1,44 @@
+package channels
+
+import (
+	"context"
+	"encoding/json"
+	"log/slog"
+
+	"github.com/redis/go-redis/v9"
+
+	"git.omukk.dev/wrenn/wrenn/pkg/events"
+)
+
+const streamKey = "wrenn:events"
+
+// Publisher pushes events onto the Redis stream for the dispatcher to consume.
+type Publisher struct {
+	rdb *redis.Client
+}
+
+// NewPublisher constructs an event publisher.
+func NewPublisher(rdb *redis.Client) *Publisher {
+	return &Publisher{rdb: rdb}
+}
+
+// Publish serializes the event and appends it to the global stream.
+// Fire-and-forget: failures are logged, never propagated.
+func (p *Publisher) Publish(ctx context.Context, e events.Event) {
+	payload, err := json.Marshal(e)
+	if err != nil {
+		slog.Warn("channels: failed to marshal event", "event", e.Event, "error", err)
+		return
+	}
+
+	if err := p.rdb.XAdd(ctx, &redis.XAddArgs{
+		Stream: streamKey,
+		MaxLen: 10000,
+		Approx: true,
+		Values: map[string]interface{}{
+			"payload": string(payload),
+		},
+	}).Err(); err != nil {
+		slog.Warn("channels: failed to publish event", "event", e.Event, "error", err)
+	}
+}