Introduces GET /api/connections and POST /api/connections/probe as the
backend half of the one-ledger / one-editor connection redesign.
- GET /api/connections aggregates PVE/PBS/PMG/VMware/TrueNAS/agent rows
into a unified Connection shape with derived state (active, paused,
unauthorized, unreachable, stale, pending) computed from in-memory
scheduler health plus agent Host.LastSeen. No new persisted state.
- POST /api/connections/probe fingerprints a host across the five
supported products in parallel (2s dial + 1s read, 3s total, max 5
concurrent). Admin-gated (RequireAdmin + ScopeSettingsWrite) to block
unauthenticated SSRF against internal hosts.
- Disabled bool on PVEInstance/PBSInstance/PMGInstance (zero-value =
enabled, preserves existing nodes.json); pollers skip disabled
instances at client init, reconnect, and per-node iteration.
- NodeConfigRequest/Response gain Enabled; write path translates
*bool -> Disabled so omitted field leaves state untouched.
- ConnectionsAPI frontend client (list/probe) typed off the Go shape.
Contracts updated: api-contracts, monitoring, agent-lifecycle,
performance-and-scalability, storage-recovery. Proofs added:
contract_test.go JSON snapshot for Connection and ProbeResponse,
monitoring guardrails for the Disabled-skip behavior, and a vitest
mock-client test for ConnectionsAPI.
Frontend editor / drawer / table rewrite lands in a separate block.
