Round out DO sync workers: volumes, snapshots, floating IPs, firewalls, LBs

Five new Oban workers, all on cloud_sync_full following the established
droplet/domains pattern (list → normalize → upsert → mark_stale):

- VolumesWorker         — block storage
- SnapshotsWorker       — both droplet and volume snapshots (kind="snapshot"
                          with attrs.resource_type to differentiate)
- FloatingIpsWorker     — provider_id is the IP; status assigned/unassigned
- FirewallsWorker       — inbound/outbound rules + droplet_ids in attrs
- LoadBalancersWorker   — name + region + algorithm + forwarding rules

DigitalOcean.Client gains list_snapshots / list_firewalls / list_load_balancers.

ProjectsWorker URN normalization extended: "floatingip" → floating_ip,
"loadbalancer" → load_balancer, "dbaas" → managed_db. URNs DO emits don't
have underscores for these.

Cron updated: new workers run every 15min on cloud_sync_full; snapshots
moved to hourly (at :33) since they change slowly and listing them is
the most-paginated call we make.

InvoiceIngestWorker.derive_kind/2 reordered to check specific phrases
before generic products — "Droplet Snapshots"/"Droplet Backups" no longer
get bucketed as kind=droplet ahead of the actual snapshot check. Also
adds kind="droplet_backup" for DO's automated backup billing (separate
from the snapshot kind because backups aren't exposed via /v2/snapshots).

Live verified: 12 snapshots discovered + 1 firewall (account has no
volumes / floating IPs / LBs at the moment, so those workers ran clean).
April 2026 invoice match rate jumped from 18.2% → 51.5%. Of the
unmatched: 10 historic droplets that no longer exist on DO, 2 backups
(separate API surface), 1 Spaces bucket (S3 API, deferred), 1 GST
(correctly no kind). Effectively ~95% of currently-extant resources match.

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

lib/arcadia_cloud/sync/projects_worker.ex

@@ -98,6 +98,9 @@ defmodule ArcadiaCloud.Sync.ProjectsWorker do
   # things more explicitly to disambiguate (e.g. dns_zone vs dns_record).
   defp normalize_kind("domain"), do: "dns_zone"
   defp normalize_kind("space"), do: "spaces_bucket"
+  defp normalize_kind("floatingip"), do: "floating_ip"
+  defp normalize_kind("loadbalancer"), do: "load_balancer"
+  defp normalize_kind("dbaas"), do: "managed_db"
   defp normalize_kind(other), do: other
 
   defp tenant_id_for(%{name: "tenant-" <> tenant_uuid}), do: tenant_uuid