Restore managed C-Gate LAN access and release 1.34.7

[dougrathbone]

Summary

Fixes #104: after an add-on upgrade, C-Bus Toolkit and other LAN clients could not reach managed C-Gate. Home Assistant left the C-Gate ports unpublished unless they were remapped, and Docker NAT often presented the PC as the container gateway so access.txt never matched.

This PR also lands Dependabot #101 (Alpine 3.24 builder) and #103 (QEMU 4.3.0 and action-gh-release 3.0.3), and bumps the add-on to 1.34.7.

Changes

• Publish C-Gate ports 20023-20025 and 20123-20125 on the host by default. Disable unused ones in the Network panel. C-Gate still refuses anyone not in cgate_external_clients.
• When external clients are listed, also grant the Docker default gateway at the highest configured level so SNATted Toolkit connections match.
• Alpine 3.24 for the npm-ci builder only; runtime stays on Home Assistant 3.21 bases.
• Pin docker/setup-qemu-action v4.3.0 and softprops/action-gh-release v3.0.3.
• Release 1.34.7.

Supersedes #101 and #103.

Test plan

• npm test passes locally (3088 tests)
• npm run lint and npm run typecheck pass
• New access-control tests for NAT gateway grant, public-gateway rejection, duplicate skip, and no grant without clients
• Addon integration asserts C-Gate ports are numeric host defaults, 8080 stays unmapped