DOCFIX-163: Office1-local network module + OPNsense edge ownership (gaps #12+16) ...

New opentofu/modules/office1-network (dc-planes-shaped, one shared network
instead of six), instantiated for real in main.tf -- deliberately not a
reused host bridge, since that would live outside OpenTofu's D-103
inventory and break the virsh net-list --all completeness check used
throughout the runbooks. Decided gap #16: Office1 gets its own OPNsense
edge (a fourth site), owned by Stage 2's runbook (new Step 4b). Found a
deeper cross-site gap while wiring the edge's WAN side (no per-site
ISP-uplink network exists for ANY site yet, DC1/DC2 included) -- logged as
new gap #17 rather than defaulted to a mesh-link, which would contradict
D-100's management-only ruling for those legs.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QrcJx8TUar7pYAvpGJw57A