feat(api): Add network bridge lifecycle management

[pparage]

Context

The API has generic node network interface add/delete, but no explicit bridge creation/deletion endpoints. The deployer UI creates bridges during deployment but has no dedicated API for managing them.

Requirements

• POST /v0/admin/proxmox/network/node/{node}/bridge/create — Create a Linux bridge with configurable VLAN awareness, IP, CIDR
• DELETE /v0/admin/proxmox/network/node/{node}/bridge/delete — Delete a bridge by name
• GET /v0/admin/proxmox/network/node/{node}/bridge/list — List bridges only (filtered from full interface list)

Priority

Important — needed for clean teardown workflows.

References

• Gap analysis: gap-analysis.md issue B10