Phase 0 scaffold: arcadia-cloud Phoenix service

API-only Phoenix 1.8 project for cloud-ops, inventory, billing, and
provisioning sagas. Validates arcadia JWTs via shared Guardian secret
(verify-only; arcadia-app remains the issuer).

Deps beyond default Phoenix: guardian, cors_plug, oban, req.
Postgres on local port 5433 per arcadia stack convention.
Endpoint runs on :4005.

Endpoints:
- GET /api/health         — public, returns service identifier
- GET /api/v1/inventory   — auth-gated, returns empty list (phase 0 stub)

Oban configured with the queues phase 1+ will need:
provisioning / cloud_sync_fast|full|slow / cloud_billing / metering.

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

lib/arcadia_cloud_web/endpoint.ex

@@ -0,0 +1,56 @@
+defmodule ArcadiaCloudWeb.Endpoint do
+  use Phoenix.Endpoint, otp_app: :arcadia_cloud
+
+  # The session will be stored in the cookie and signed,
+  # this means its contents can be read but not tampered with.
+  # Set :encryption_salt if you would also like to encrypt it.
+  @session_options [
+    store: :cookie,
+    key: "_arcadia_cloud_key",
+    signing_salt: "Ia2pTcnv",
+    same_site: "Lax"
+  ]
+
+  # socket "/live", Phoenix.LiveView.Socket,
+  #   websocket: [connect_info: [session: @session_options]],
+  #   longpoll: [connect_info: [session: @session_options]]
+
+  # Serve at "/" the static files from "priv/static" directory.
+  #
+  # When code reloading is disabled (e.g., in production),
+  # the `gzip` option is enabled to serve compressed
+  # static files generated by running `phx.digest`.
+  plug Plug.Static,
+    at: "/",
+    from: :arcadia_cloud,
+    gzip: not code_reloading?,
+    only: ArcadiaCloudWeb.static_paths(),
+    raise_on_missing_only: code_reloading?
+
+  # Code reloading can be explicitly enabled under the
+  # :code_reloader configuration of your endpoint.
+  if code_reloading? do
+    plug Phoenix.CodeReloader
+    plug Phoenix.Ecto.CheckRepoStatus, otp_app: :arcadia_cloud
+  end
+
+  plug Plug.RequestId
+  plug Plug.Telemetry, event_prefix: [:phoenix, :endpoint]
+
+  plug Plug.Parsers,
+    parsers: [:urlencoded, :multipart, :json],
+    pass: ["*/*"],
+    json_decoder: Phoenix.json_library()
+
+  plug Plug.MethodOverride
+  plug Plug.Head
+  plug Plug.Session, @session_options
+
+  plug CORSPlug,
+    origin: [
+      "http://localhost:5173",
+      ~r{^https://.*\.sky-ai\.com$}
+    ]
+
+  plug ArcadiaCloudWeb.Router
+end