fix(persistence): migrate all pkg/persistence imports to plugins/infra/database and plugins/infra/cache

- Replace db.DB(ctx) with database.DB(ctx) from plugins/infra/database
- Replace db.Redis/db.PrefixedKey/db.GetJSON/db.SetJSON with cachepkg.* from plugins/infra/cache
- Replace pkg/persistence/idgen with pkg/idgen (already exists)
- Replace pkg/persistence/batchwriter with pkg/batchwriter (already exists)
- Replace pkg/persistence/migrator with pkg/migrator (already exists)
- Replace pkg/persistence/logstore with plugins/domain/risk_control/logstore
- Delete defunct pkg/{persistence,cap,message_gateway,push,shared,task}
- Fix vet issues: db alias in domain_test.go, driver_asynq_worker.TaskHandler reference
- Update Makefile architecture guard
- Update docs and skill references
- Update go.mod: gorilla/sessions promotion to direct dependency

plugins/domain/message_gateway/channel.go

@@ -0,0 +1,21 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package message_gateway
+
+import "context"
+
+// Handler processes one inbound message.
+type Handler func(ctx context.Context, msg InboundMessage) error
+
+// Factory constructs a Channel from decrypted config.
+type Factory func(cfg ChannelConfig, onInbound Handler) (Channel, error)
+
+// Channel is one connected messaging adapter.
+type Channel interface {
+	Type() string
+	Connect(ctx context.Context) error
+	Disconnect(ctx context.Context) error
+	Send(ctx context.Context, to Recipient, msg OutboundMessage) error
+	Capabilities() Capability
+}