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/digital_ocean/tokens.ex

@@ -0,0 +1,24 @@
+defmodule ArcadiaCloud.DigitalOcean.Tokens do
+  @moduledoc """
+  DO API token resolver. Per-purpose so worker queues use separate tokens
+  (rate limit isolation + blast radius — see project_arcadia_cloud memory).
+
+  Phase 0/1 implementation: all purposes fall back to the single
+  `DO_API_TOKEN` env var (or `:default_token` app env).
+  Phase 2: read per-purpose bundles from the secrets vault.
+  """
+
+  @env_var "DO_API_TOKEN"
+
+  def fetch(purpose) when is_binary(purpose) do
+    case resolve(purpose) do
+      nil -> {:error, :no_token_configured}
+      token -> {:ok, token}
+    end
+  end
+
+  defp resolve(_purpose) do
+    Application.get_env(:arcadia_cloud, :do_api_token) ||
+      System.get_env(@env_var)
+  end
+end