Modbus point-ID migration compatibility

The new hexadecimal point-ID design grouped slave address with Modbus type, and register address with data index. Backend generation, parsing and compatibility were centralized with passing backend tests reported. Gateway work and existing-ID rewriting continued. A separate local dev commit corrected FC03 to FC02 for discrete inputs and separated bit/register limits; 160 tests passed, without a captured push or hardware check. Legacy references in history, exports and advisor snapshots were to remain resolvable, with resumable rewriting planned and production scale unknown.

A real import API exercised against an isolated database distinguished Modbus types at the same address. Y301-110, Y301-220, Y301-440 and Y301-880 templates were then corrected for an offset caused by incrementing both address and data index. Reports covered production-template readback, offline message checks, backup and an operation log. The templates affect future imports, not existing device points automatically. Real device traffic and the complete historical-ID migration were not accepted.