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

Makefile

@@ -36,8 +36,8 @@ build-embedded:
 code-check:
 	@echo "==> Architecture guards..."
 	@command -v rg >/dev/null 2>&1 || { echo 'error: rg (ripgrep) is required for architecture guards' >&2; exit 1; }
-	@if [ -d pkg/model ] && rg -n 'db\.DB\(|db\.Redis' pkg/model --glob '*.go' -g '!*_test.go' ; then \
-		echo 'error: pkg/model must not access db.DB or db.Redis (non-test code)' >&2; \
+	@if [ -d pkg/model ] && rg -n 'database\.DB\(|cachepkg\.Redis' pkg/model --glob '*.go' -g '!*_test.go' ; then \
+		echo 'error: pkg/model must not access database.DB or cachepkg.Redis (non-test code)' >&2; \
 		exit 1; \
 	fi
 	golangci-lint run