make PDP variant selection work without JS

Variant options (colour, size) are now URL params handled via
handle_params instead of phx-click events. Swatches and size buttons
render as patch links in shop mode, so changing variants works as
plain navigation without JS. Quantity is now a number input that
submits with the form. Unavailable variants render as disabled spans.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/berrypod_web/components/shop_components/product.ex

@@ -1339,13 +1339,15 @@ defmodule BerrypodWeb.ShopComponents.Product do
   Renders a variant selector for a single option type.
 
   Shows color swatches for color-type options, text buttons for others.
-  Disables unavailable options and fires `select_option` event on click.
+  In shop mode, each option is a patch link for progressive enhancement.
+  In preview mode, options are inert buttons.
 
   ## Attributes
 
   * `option_type` - Required. Map with :name, :type, :values keys
   * `selected` - Required. Currently selected value (string)
   * `available` - Required. List of available values for this option
+  * `option_urls` - Optional. Map of value title => patch URL
   * `mode` - Optional. :shop or :preview (default: :shop)
 
   ## Examples
@@ -1354,11 +1356,13 @@ defmodule BerrypodWeb.ShopComponents.Product do
         option_type={%{name: "Size", type: :size, values: [%{title: "S"}, ...]}}
         selected="M"
         available={["S", "M", "L"]}
+        option_urls={%{"S" => "/products/foo?Size=S", ...}}
       />
   """
   attr :option_type, :map, required: true
   attr :selected, :string, required: true
   attr :available, :list, required: true
+  attr :option_urls, :map, default: %{}
   attr :mode, :atom, default: :shop
 
   def variant_selector(assigns) do
@@ -1378,8 +1382,8 @@ defmodule BerrypodWeb.ShopComponents.Product do
             hex={value[:hex] || "#888888"}
             selected={value.title == @selected}
             disabled={value.title not in @available}
-            option_name={@option_type.name}
             mode={@mode}
+            url={@option_urls[value.title]}
           />
         <% else %>
           <.size_button
@@ -1387,8 +1391,8 @@ defmodule BerrypodWeb.ShopComponents.Product do
             title={value.title}
             selected={value.title == @selected}
             disabled={value.title not in @available}
-            option_name={@option_type.name}
             mode={@mode}
+            url={@option_urls[value.title]}
           />
         <% end %>
       </div>
@@ -1400,44 +1404,76 @@ defmodule BerrypodWeb.ShopComponents.Product do
   attr :hex, :string, required: true
   attr :selected, :boolean, required: true
   attr :disabled, :boolean, required: true
-  attr :option_name, :string, required: true
   attr :mode, :atom, default: :shop
+  attr :url, :string, default: nil
 
   defp color_swatch(assigns) do
     ~H"""
-    <button
-      type="button"
-      phx-click={if @mode == :shop, do: "select_option"}
-      phx-value-option={@option_name}
-      phx-value-selected={@title}
-      class="color-swatch"
-      style={"background-color: #{@hex};"}
-      title={@title}
-      aria-label={"Select #{@title}"}
-      aria-pressed={to_string(@selected)}
-    >
-    </button>
+    <%= cond do %>
+      <% @mode == :shop and not @disabled -> %>
+        <.link
+          patch={@url}
+          class="color-swatch"
+          style={"background-color: #{@hex};"}
+          title={@title}
+          aria-label={"Select #{@title}"}
+          aria-pressed={to_string(@selected)}
+        >
+        </.link>
+      <% @mode == :shop -> %>
+        <span
+          class="color-swatch"
+          style={"background-color: #{@hex};"}
+          title={"#{@title} (unavailable)"}
+          aria-label={"#{@title} (unavailable)"}
+          aria-disabled="true"
+        />
+      <% true -> %>
+        <button
+          type="button"
+          class="color-swatch"
+          style={"background-color: #{@hex};"}
+          title={@title}
+          aria-label={"Select #{@title}"}
+          aria-pressed={to_string(@selected)}
+        />
+    <% end %>
     """
   end
 
   attr :title, :string, required: true
   attr :selected, :boolean, required: true
   attr :disabled, :boolean, required: true
-  attr :option_name, :string, required: true
   attr :mode, :atom, default: :shop
+  attr :url, :string, default: nil
 
   defp size_button(assigns) do
     ~H"""
-    <button
-      type="button"
-      phx-click={if @mode == :shop, do: "select_option"}
-      phx-value-option={@option_name}
-      phx-value-selected={@title}
-      class="size-btn"
-      aria-pressed={to_string(@selected)}
-    >
-      {@title}
-    </button>
+    <%= cond do %>
+      <% @mode == :shop and not @disabled -> %>
+        <.link
+          patch={@url}
+          class="size-btn"
+          aria-pressed={to_string(@selected)}
+        >
+          {@title}
+        </.link>
+      <% @mode == :shop -> %>
+        <span
+          class="size-btn"
+          aria-disabled="true"
+        >
+          {@title}
+        </span>
+      <% true -> %>
+        <button
+          type="button"
+          class="size-btn"
+          aria-pressed={to_string(@selected)}
+        >
+          {@title}
+        </button>
+    <% end %>
     """
   end
 
@@ -1478,9 +1514,15 @@ defmodule BerrypodWeb.ShopComponents.Product do
           >
             −
           </button>
-          <span class="qty-display">
-            {@quantity}
-          </span>
+          <input
+            type="number"
+            name="quantity"
+            value={@quantity}
+            min={@min}
+            max={@max}
+            class="qty-display"
+            aria-label="Quantity"
+          />
           <button
             type="button"
             phx-click="increment_quantity"