OpenWrt Support for MikroTik RB1100AHx4 (Annapurna Labs Alpine)

I’ve been working on initial OpenWrt support for the MikroTik RB1100AHx4, based on the Annapurna Labs Alpine platform.

This PR adds a new Alpine target and includes early RB1100AHx4 support.

Current status on real hardware:

* boots to userspace * DSA switch path is working * LAN forwarding works * ping works after network setup

What is still incomplete:

* NAND/sysupgrade is intentionally disabled for now * flash layout and safe persistent upgrade flow still need work * the platform still needs review for structure, maintainability, and upstream suitability

I’m posting this mainly to get technical feedback from people interested in OpenWrt, embedded Linux, DSA, and older Annapurna Labs hardware.

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