feat: ship loose-offline dbsync (validate, agent push, LWW audit)

Add UUID/FK channel checks, agent whitelist/push APIs, bindings, super-admin LWW audit with rollback, reconcile rate limits, and sync docs. Default customers stay opt-in; company conflict UI is removed.

Co-authored-by: Cursor <cursoragent@cursor.com>

platform/internal/dbsync/lww_audit.go

@@ -0,0 +1,41 @@
+package dbsync
+
+import (
+	"context"
+	"database/sql"
+	"time"
+)
+
+const (
+	EntryDrain     = "drain"
+	EntryAgentPush = "agent_push"
+	EntryRollback  = "rollback"
+	OutcomeApplied = "applied_source"
+	OutcomeKept    = "kept_target"
+	OutcomeRolled  = "rolled_back"
+)
+
+// RecordLwwOverride 在 LWW 覆盖或保留目标时写入超管审计（失败忽略，不挡同步）。
+func RecordLwwOverride(store *FileStore, o LwwOverride) {
+	if store == nil {
+		return
+	}
+	_ = store.AddLwwOverride(o)
+}
+
+// SnapshotTargetRow 取目标端当前行 JSON（无行则空串）。
+func SnapshotTargetRow(ctx context.Context, db *sql.DB, driver Driver, table, pkCol, rowPK string) string {
+	if db == nil || rowPK == "" {
+		return ""
+	}
+	js, _, err := FetchRowJSON(ctx, db, driver, table, pkCol, rowPK)
+	if err != nil {
+		return ""
+	}
+	return js
+}
+
+// DefaultLwwAuditTTL 默认 90 天。
+func DefaultLwwAuditTTL() time.Duration {
+	return 90 * 24 * time.Hour
+}