Phase 3: pricing catalog

Five catalog tables:
- plans            — plan identity (code, name); the stable thing.
- plan_versions    — versioned pricing (base_price_cents, currency,
                     status draft/active/retired). A subscription binds
                     to a version; raising prices = publish a new
                     version, existing subs unaffected until migrated.
- plan_items       — what a version includes per resource_kind, plus
                     overage terms (overage_unit, overage_price_cents,
                     hard_cap_qty).
- addons           — a la carte upgrades (code, resource_kind, qty,
                     price_cents).
- resource_prices  — effective-dated fallback per-unit pricing for
                     ad-hoc items not covered by a plan.

ArcadiaCloud.Catalog context: plan + version CRUD, active_version/1
(what a new signup gets), publish_version/1 (retires the prior active
version transactionally then activates the new one),
current_resource_price/2 (effective-dated lookup).

Seed (priv/repo/seeds/catalog_seed.exs, idempotent) creates three AUD
plans — Starter $20, Studio $50, Pro $120/mo — with included
droplet_hours / spaces_gb_month / snapshot_gb_month / bandwidth_gb /
dns_zones (and LLM token allowances on Studio + Pro), plus three storage
/ LLM addons. Prices are placeholders to tune against real DO COGS once
the cost-vs-revenue dashboard lands.

API (authenticated tenants — the catalog is what they pick from):
- GET /api/v1/catalog/plans   — plans with active version + items
- GET /api/v1/catalog/addons

Smoke verified: seed creates 3 plans + 3 addons; endpoints return the
shaped catalog.

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

lib/arcadia_cloud/catalog.ex

@@ -0,0 +1,133 @@
+defmodule ArcadiaCloud.Catalog do
+  @moduledoc """
+  Pricing catalog — plans, versioned pricing, plan items (included
+  resources + overage), addons, fallback resource prices.
+
+  Versioning: a subscription binds to a specific plan_version. Raising
+  prices = publish a new version; existing subs are unaffected until
+  explicitly migrated. `active_version/1` returns the version new
+  signups get.
+  """
+
+  import Ecto.Query, warn: false
+
+  alias ArcadiaCloud.Repo
+  alias ArcadiaCloud.Catalog.{Plan, PlanVersion, PlanItem, Addon, ResourcePrice}
+
+  # ---- plans ----------------------------------------------------------------
+
+  def list_plans do
+    from(p in Plan, where: p.active == true, order_by: p.code)
+    |> Repo.all()
+  end
+
+  def get_plan_by_code(code) do
+    Repo.get_by(Plan, code: code)
+  end
+
+  def create_plan(attrs) do
+    %Plan{}
+    |> Plan.changeset(attrs)
+    |> Repo.insert()
+  end
+
+  # ---- versions -------------------------------------------------------------
+
+  @doc "The version a new subscription to this plan would get."
+  def active_version(%Plan{id: plan_id}), do: active_version(plan_id)
+
+  def active_version(plan_id) when is_binary(plan_id) do
+    from(v in PlanVersion,
+      where: v.plan_id == ^plan_id and v.status == "active",
+      order_by: [desc: v.version],
+      limit: 1,
+      preload: [:items]
+    )
+    |> Repo.one()
+  end
+
+  def get_version!(id), do: Repo.get!(PlanVersion, id) |> Repo.preload([:items, :plan])
+
+  def get_version(id) do
+    case Repo.get(PlanVersion, id) do
+      nil -> nil
+      v -> Repo.preload(v, [:items, :plan])
+    end
+  end
+
+  def next_version_number(plan_id) do
+    max =
+      from(v in PlanVersion, where: v.plan_id == ^plan_id, select: max(v.version))
+      |> Repo.one()
+
+    (max || 0) + 1
+  end
+
+  def create_version(attrs) do
+    %PlanVersion{}
+    |> PlanVersion.changeset(attrs)
+    |> Repo.insert()
+  end
+
+  @doc """
+  Publishes a draft version: retires any currently-active version of the
+  same plan, then flips this one to active.
+  """
+  def publish_version(%PlanVersion{} = version) do
+    now = DateTime.utc_now() |> DateTime.truncate(:second)
+
+    Repo.transaction(fn ->
+      from(v in PlanVersion,
+        where: v.plan_id == ^version.plan_id and v.status == "active"
+      )
+      |> Repo.update_all(set: [status: "retired", updated_at: now])
+
+      version
+      |> PlanVersion.changeset(%{status: "active", published_at: now})
+      |> Repo.update!()
+    end)
+  end
+
+  # ---- plan items -----------------------------------------------------------
+
+  def add_plan_item(attrs) do
+    %PlanItem{}
+    |> PlanItem.changeset(attrs)
+    |> Repo.insert()
+  end
+
+  # ---- addons ---------------------------------------------------------------
+
+  def list_addons do
+    from(a in Addon, where: a.active == true, order_by: a.code) |> Repo.all()
+  end
+
+  def get_addons(codes) when is_list(codes) do
+    from(a in Addon, where: a.code in ^codes) |> Repo.all()
+  end
+
+  def create_addon(attrs) do
+    %Addon{}
+    |> Addon.changeset(attrs)
+    |> Repo.insert()
+  end
+
+  # ---- resource prices ------------------------------------------------------
+
+  def current_resource_price(resource_kind, on_date \\ Date.utc_today()) do
+    from(p in ResourcePrice,
+      where:
+        p.resource_kind == ^resource_kind and p.effective_from <= ^on_date and
+          (is_nil(p.effective_to) or p.effective_to >= ^on_date),
+      order_by: [desc: p.effective_from],
+      limit: 1
+    )
+    |> Repo.one()
+  end
+
+  def create_resource_price(attrs) do
+    %ResourcePrice{}
+    |> ResourcePrice.changeset(attrs)
+    |> Repo.insert()
+  end
+end