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/infra/storage/objectstore/storage_test.go

@@ -11,7 +11,7 @@ import (
 	"testing"
 	"time"
 
-	"github.com/Rain-kl/Wavelet/pkg/persistence"
+	cache "github.com/Rain-kl/Wavelet/plugins/infra/cache"
 	"github.com/alicebob/miniredis/v2"
 	"github.com/redis/go-redis/v9"
 )
@@ -91,11 +91,11 @@ func TestStorageCachePubSub(t *testing.T) {
 	})
 	defer rdb.Close()
 
-	// 3. Set db.Redis to our client
-	oldRedis := db.Redis
-	db.Redis = rdb
+	// 3. Set cache.Redis to our client
+	oldRedis := cache.Redis
+	cache.Redis = rdb
 	defer func() {
-		db.Redis = oldRedis
+		cache.Redis = oldRedis
 	}()
 
 	// Reset cache and set some cached config