feat: add Settings and Media contexts with theme settings schema

- Create settings table for site-wide key-value configuration
- Create images table for BLOB storage of logo/header images
- Add Setting schema with JSON/string/integer/boolean support
- Add ThemeSettings embedded schema with all theme options
- Add Settings context with get/put/update operations
- Add Media context for image uploads and retrieval
- Add Image schema with SVG detection and storage
- Add 9 curated theme presets (gallery, studio, boutique, etc.)
- Add comprehensive tests for Settings and Media contexts
- Add seeds with default Studio preset
- All tests passing (29 tests, 0 failures)

lib/simpleshop_theme/theme/presets.ex

@@ -0,0 +1,135 @@
+defmodule SimpleshopTheme.Theme.Presets do
+  @moduledoc """
+  Defines the 9 curated theme presets for SimpleShop.
+  """
+
+  @presets %{
+    gallery: %{
+      mood: "warm",
+      typography: "editorial",
+      shape: "soft",
+      density: "spacious",
+      grid_columns: "3",
+      header_layout: "centered",
+      accent_color: "#e85d04"
+    },
+    studio: %{
+      mood: "neutral",
+      typography: "clean",
+      shape: "soft",
+      density: "balanced",
+      grid_columns: "4",
+      header_layout: "standard",
+      accent_color: "#3b82f6"
+    },
+    boutique: %{
+      mood: "warm",
+      typography: "classic",
+      shape: "soft",
+      density: "balanced",
+      grid_columns: "3",
+      header_layout: "centered",
+      accent_color: "#b45309"
+    },
+    bold: %{
+      mood: "neutral",
+      typography: "modern",
+      shape: "sharp",
+      density: "compact",
+      grid_columns: "4",
+      header_layout: "standard",
+      accent_color: "#dc2626"
+    },
+    playful: %{
+      mood: "neutral",
+      typography: "friendly",
+      shape: "pill",
+      density: "balanced",
+      grid_columns: "4",
+      header_layout: "standard",
+      accent_color: "#8b5cf6"
+    },
+    minimal: %{
+      mood: "cool",
+      typography: "minimal",
+      shape: "sharp",
+      density: "spacious",
+      grid_columns: "2",
+      header_layout: "minimal",
+      accent_color: "#171717"
+    },
+    night: %{
+      mood: "dark",
+      typography: "modern",
+      shape: "soft",
+      density: "balanced",
+      grid_columns: "4",
+      header_layout: "standard",
+      accent_color: "#f97316"
+    },
+    classic: %{
+      mood: "warm",
+      typography: "classic",
+      shape: "soft",
+      density: "spacious",
+      grid_columns: "3",
+      header_layout: "standard",
+      accent_color: "#166534"
+    },
+    impulse: %{
+      mood: "neutral",
+      typography: "impulse",
+      shape: "sharp",
+      density: "spacious",
+      grid_columns: "3",
+      header_layout: "centered",
+      accent_color: "#000000",
+      font_size: "medium",
+      heading_weight: "regular",
+      layout_width: "full",
+      button_style: "filled",
+      card_shadow: "none",
+      product_text_align: "center"
+    }
+  }
+
+  @doc """
+  Returns all available presets.
+
+  ## Examples
+
+      iex> all()
+      %{gallery: %{...}, studio: %{...}, ...}
+
+  """
+  def all, do: @presets
+
+  @doc """
+  Gets a preset by name.
+
+  ## Examples
+
+      iex> get(:gallery)
+      %{mood: "warm", typography: "editorial", ...}
+
+      iex> get(:nonexistent)
+      nil
+
+  """
+  def get(preset_name) when is_atom(preset_name) do
+    Map.get(@presets, preset_name)
+  end
+
+  @doc """
+  Lists all preset names.
+
+  ## Examples
+
+      iex> list_names()
+      [:gallery, :studio, :boutique, :bold, :playful, :minimal, :night, :classic, :impulse]
+
+  """
+  def list_names do
+    Map.keys(@presets)
+  end
+end