Add JSON REST API for MCP integration

- Add /api/v1 namespace with Bearer token auth (PINCHFLAT_API_TOKEN env var)
- API controllers for sources, media items, media profiles, settings, tasks
- Support for all source actions: create, update, delete, force_download_pending,
  force_redownload, force_index, force_metadata_refresh, sync_files_on_disk
- Media item endpoints: list, show, search, force_download, update, delete
- Media profile CRUD endpoints
- Settings show/update and app_info endpoints
- Task listing endpoints
- Add Jason.Encoder for Task schema
- Comprehensive test suite for all API endpoints
- Gitea Actions CI workflow (runs existing checks + API-specific tests)
- API documentation in docs/API.md

lib/pinchflat_web/controllers/api/v1/api_setting_controller.ex

@@ -0,0 +1,56 @@
+defmodule PinchflatWeb.Api.V1.ApiSettingController do
+  @moduledoc """
+  JSON API controller for Settings.
+  """
+
+  use PinchflatWeb, :controller
+
+  alias Pinchflat.Settings
+
+  def show(conn, _params) do
+    setting = Settings.record()
+    safe_data = setting_to_map(setting)
+    json(conn, %{data: safe_data})
+  end
+
+  def update(conn, %{"setting" => params}) do
+    setting = Settings.record()
+
+    case Settings.update_setting(setting, params) do
+      {:ok, setting} ->
+        safe_data = setting_to_map(setting)
+        json(conn, %{data: safe_data})
+
+      {:error, %Ecto.Changeset{} = changeset} ->
+        conn
+        |> put_status(:unprocessable_entity)
+        |> json(%{errors: format_changeset_errors(changeset)})
+    end
+  end
+
+  def app_info(conn, _params) do
+    info = %{
+      version: Application.spec(:pinchflat, :vsn) |> to_string(),
+      environment: Application.get_env(:pinchflat, :env),
+      yt_dlp_version: Settings.get!(:yt_dlp_version),
+      apprise_version: Settings.get!(:apprise_version),
+      onboarding: Settings.get!(:onboarding)
+    }
+
+    json(conn, %{data: info})
+  end
+
+  defp setting_to_map(setting) do
+    setting
+    |> Map.from_struct()
+    |> Map.drop([:route_token, :__meta__, :__struct__])
+  end
+
+  defp format_changeset_errors(changeset) do
+    Ecto.Changeset.traverse_errors(changeset, fn {msg, opts} ->
+      Enum.reduce(opts, msg, fn {key, value}, acc ->
+        String.replace(acc, "%{#{key}}", to_string(value))
+      end)
+    end)
+  end
+end