BSDnas v0.1.2-dev — FreeBSD stable/15 refresh, unattended install and upgrade

Development pre-release built from BSDnas-15-MASTER-202608191412.

Highlights since v0.1.1-dev:

• FreeBSD base updated to the latest stable/15 (284 upstream commits merged).
• Fully unattended network install: the installer reports completion back
  to the install server, including the machine address and the activated
  boot environment; no console interaction is required, including the
  former swap-confirmation dialog.
• Upgrades install into a new boot environment and never touch data
  pools; boot environment activation is honored on network-chained boots.
• System installs onto the data-array disks (bootsize/bootmirror), with
  a spare boot partition kept on the extra disk.

Verify the image with SHA256SUMS and its detached signature
(BSDnas-signing-key.asc, ed25519 fingerprint
58528D1CDBDAAF7B01ED2BBE1E2F7A792066322D).