Phase 1 continued: ProjectsWorker, DomainsWorker, Oban Cron schedule

ProjectsWorker mirrors DO Projects to cloud_projects table in a two-pass
sweep: upsert projects, then walk each project's resource membership
(list_project_resources) and update cloud_resources.cloud_project_id +
tenant_id. DO URN kinds get normalized via normalize_kind/1 (domain →
dns_zone, space → spaces_bucket) so attribution matches local naming.

DomainsWorker syncs DNS zones (DO Domains). Same upsert chokepoint, same
three-strike stale handling. Zones are global to the account; attribution
happens via ProjectsWorker if a domain is in a DO project, else stays
NULL pending operator classification.

Oban.Plugins.Cron added with 15-minute schedules for ProjectsWorker,
DropletsWorker, DomainsWorker — workers run automatically once a token
is configured. Phase 0/1 cadence; phase 2 moves droplets to cloud_sync_fast
(1-min) for real-time status visibility.

DigitalOcean.Client gains list_domains / list_volumes / list_floating_ips.
Volumes and floating IPs not yet wired to workers; trivial follow-on.

Live smoke test: 5 droplets + 7 DNS zones discovered, all attributed to
their existing DO projects via membership lookup (skyai-internal becomes
the fallback only for genuinely orphan resources).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/arcadia_cloud/digital_ocean/client.ex

@@ -17,6 +17,9 @@ defmodule ArcadiaCloud.DigitalOcean.Client do
 
   def list_droplets(opts \\ []), do: list_paginated("/droplets", "droplets", opts)
   def list_projects(opts \\ []), do: list_paginated("/projects", "projects", opts)
+  def list_domains(opts \\ []), do: list_paginated("/domains", "domains", opts)
+  def list_volumes(opts \\ []), do: list_paginated("/volumes", "volumes", opts)
+  def list_floating_ips(opts \\ []), do: list_paginated("/floating_ips", "floating_ips", opts)
 
   def create_project(name, purpose, description \\ "", opts \\ []) do
     body = %{