replace Tailwind in content + collection, remove shop Tailwind entirely (Phase 5c)

- Replace all Tailwind utilities in content.ex and collection.ex with
  semantic CSS classes (content body, contact form, cards, reviews, etc.)
- Delete app-shop.css (Tailwind shop entry point)
- Remove shop Tailwind config from config.exs, dev.exs, mix.exs
- Remove shop Tailwind stylesheet link from shop_root.html.heex
- Add collection filter bar, empty state, and select dropdown styles
- Fix filter pill sizing (use theme font vars instead of hardcoded rem)
- Fix active pill contrast (tinted accent background + dark accent text)
- Fix --t-text-on-accent fallback for pill legibility
- Add padding/font-size to .themed-select

Shop pages now use zero Tailwind. Admin Tailwind remains for Phase 6.

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

lib/mix/tasks/screenshots.ex

@@ -159,7 +159,6 @@ defmodule Mix.Tasks.Screenshots do
     Mix.shell().info("Building production assets...")
 
     Mix.Task.run("tailwind", ["simpleshop_theme", "--minify"])
-    Mix.Task.run("tailwind", ["simpleshop_theme_shop", "--minify"])
     Mix.Task.run("esbuild", ["simpleshop_theme", "--minify"])
     Mix.Task.run("esbuild", ["simpleshop_theme_shop_css", "--minify"])
     Mix.Task.run("phx.digest")