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.

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

docs/api/openapi.yaml

@@ -5216,7 +5216,7 @@ paths:
       tags:
         - Agents
       summary: Update node agent
-      description: Partial update — accepts any subset of agent fields (name, status, auto_prune, tags). `tags` sets the node's placement labels; services with placement_tags only schedule onto agents carrying every required tag.
+      description: Partial update — accepts any subset of agent fields (name, status, auto_prune, tags, default_domain). `tags` sets the node's placement labels; services with placement_tags only schedule onto agents carrying every required tag. `default_domain` gives the node a base domain — domainless services placed there get `<name>.<default_domain>` auto-hostnames; empty string clears it.
       security:
         - bearerAuth: []
       parameters:
@@ -9178,6 +9178,13 @@ components:
           type: array
           items: { type: string }
           description: Operator-set placement labels; services with placement_tags require all of them on the target node.
+        default_domain:
+          type: string
+          description: >-
+            Node base domain — services placed on this node (pin or spread)
+            with no explicit service_domains get `<name>.<default_domain>`
+            hostnames automatically. Wildcard DNS for `*.<default_domain>`
+            must resolve to the Containr edge.
         last_heartbeat:
           type: string
           format: date-time