feat(nodes): per-node default domain with auto service hostnames (#65)

node_agents.default_domain gives each agent a base domain. Services
placed on it (explicit pin or spread) with no explicit service_domains
get <name>.<default_domain> — resolved in serviceDomainNames so edge
routing, wake placeholders, and public_url all see the same names.
Spread services union every eligible node's base domain; explicit
domains always win.

Surfaces: PUT /agents/:id {default_domain} (hostname-validated), CLI
nodes update --domain, MCP arg docs, OpenAPI + regenerated types,
node-detail inline editor.

Also marks the already-shipped backup-import roadmap item.

Generated with [Devin](https://devin.ai)

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/database/sqlcdb/querier.go

@@ -95,6 +95,9 @@ type Querier interface {
 	// display, when the caller owns or is a member of it, or when the caller is a
 	// platform admin. Anonymous callers pass user_id = uuid.Nil, is_admin = false.
 	ListProjectsWithStatsByUser(ctx context.Context, arg ListProjectsWithStatsByUserParams) ([]ListProjectsWithStatsByUserRow, error)
+	// Base domains of every online, schedulable agent carrying the required
+	// placement tags — auto-domain candidates for spread services.
+	ListSchedulableAgentDomains(ctx context.Context, dollar_1 json.RawMessage) ([]string, error)
 	ListSchedulableAgents(ctx context.Context) ([]ListSchedulableAgentsRow, error)
 	// Only agents carrying every required placement tag (jsonb array containment).
 	ListSchedulableAgentsMatching(ctx context.Context, dollar_1 json.RawMessage) ([]ListSchedulableAgentsMatchingRow, error)
@@ -118,6 +121,7 @@ type Querier interface {
 	RevokeAgentAuthToken(ctx context.Context, id uuid.UUID) (AgentAuthToken, error)
 	RevokeUserToken(ctx context.Context, arg RevokeUserTokenParams) (int64, error)
 	ScrubCommandPayload(ctx context.Context, arg ScrubCommandPayloadParams) error
+	SetAgentDefaultDomain(ctx context.Context, arg SetAgentDefaultDomainParams) error
 	SetAgentSchedulable(ctx context.Context, arg SetAgentSchedulableParams) error
 	SetAgentTags(ctx context.Context, arg SetAgentTagsParams) error
 	SetDatabaseBackupRemoteKeyByID(ctx context.Context, arg SetDatabaseBackupRemoteKeyByIDParams) error