Phase 1 first chunk: inventory schema + DO droplet sync

Models:
- cloud_projects: arcadia-cloud's mirror of DO Projects, indexed by
  (provider, provider_id); tenant_id + purpose classify each project.
- cloud_resources: single unified resource table; kind-specific bits in
  attrs JSONB; first_seen_at / last_seen_at / stale_strike_count drive
  three-strike deletion.
- cloud_resource_events: append-only audit (discovered, updated, deleted,
  drift_detected, tagged, restored).

ArcadiaCloud.Cloud context owns the single upsert chokepoint that:
- inserts new with `discovered` event
- updates existing only when meaningful fields change
- restores tombstoned rows seen again
- bumps last_seen_at and resets strike count
mark_stale/3 implements the three-strike rule.

ArcadiaCloud.DigitalOcean.Client is a Req wrapper with auto-pagination.
Per-purpose token resolution via .Tokens (phase 1: env DO_API_TOKEN;
phase 2: vault). Per project_arcadia_cloud memory the long-term shape
is one PAT per queue purpose for rate-limit isolation.

ArcadiaCloud.Sync.Bootstrap ensures the skyai-internal DO Project exists
on first sync, idempotent thereafter. ArcadiaCloud.Sync.DropletsWorker
runs full droplet sync on the cloud_sync_full Oban queue.

InventoryController wired to real data: platform_admin sees all,
tenants see only their scope.

Live smoke test against real DO: 5 droplets synced; skyai-internal
project auto-created; events written; endpoint returns scoped results.

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

lib/arcadia_cloud/sync/bootstrap.ex

@@ -0,0 +1,51 @@
+defmodule ArcadiaCloud.Sync.Bootstrap do
+  @moduledoc """
+  First-run bootstrap: ensure the `skyai-internal` DO Project exists and
+  is registered in our `cloud_projects` table. Resources discovered before
+  any tenant project exists land here by default.
+
+  Idempotent: safe to call on every sync.
+  """
+
+  alias ArcadiaCloud.Cloud
+  alias ArcadiaCloud.DigitalOcean.Client
+
+  @internal_name "skyai-internal"
+  @internal_purpose "skyai-infra"
+  @do_purpose "Service or API"
+
+  def ensure_skyai_internal do
+    case Cloud.skyai_internal_project() do
+      %{} = project ->
+        {:ok, project}
+
+      nil ->
+        with {:ok, do_project} <- find_or_create_do_project() do
+          {:ok, _local} =
+            Cloud.ensure_project(%{
+              provider: "digitalocean",
+              provider_id: do_project["id"],
+              name: @internal_name,
+              purpose: @internal_purpose,
+              metadata: %{
+                do_purpose: do_project["purpose"],
+                description: do_project["description"]
+              }
+            })
+        end
+    end
+  end
+
+  defp find_or_create_do_project do
+    with {:ok, projects} <- Client.list_projects() do
+      case Enum.find(projects, &(&1["name"] == @internal_name)) do
+        nil ->
+          Client.create_project(@internal_name, @do_purpose,
+            "Sky AI internal infrastructure (auto-created by arcadia-cloud)")
+
+        existing ->
+          {:ok, existing}
+      end
+    end
+  end
+end