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>

assets/css/theme-semantic.css

@@ -210,23 +210,30 @@
 .collection-filter-pills {
   display: flex;
   flex-wrap: wrap;
-  gap: 0.375rem;
+  gap: 0.5rem;
 }
 
 .collection-filter-pill {
   display: inline-block;
   padding: 0.375rem 0.75rem;
   border-radius: 9999px;
-  font-size: 0.75rem;
+  font-size: var(--t-text-small);
   white-space: nowrap;
+  text-decoration: none;
   transition: opacity 0.15s;
   background-color: var(--t-surface-raised);
   color: var(--t-text-primary);
+  border: 1px solid var(--t-border-default);
+
+  &:hover:not(.active) {
+    opacity: 0.8;
+  }
 
   &.active {
-    background-color: var(--t-accent);
-    color: var(--t-text-on-accent);
-    font-weight: 500;
+    background-color: hsl(var(--t-accent-h) var(--t-accent-s) var(--t-accent-l) / 0.12);
+    color: hsl(var(--t-accent-h) var(--t-accent-s) calc(var(--t-accent-l) - 15%));
+    border-color: hsl(var(--t-accent-h) var(--t-accent-s) var(--t-accent-l) / 0.25);
+    font-weight: 600;
   }
 }
 
@@ -248,15 +255,6 @@
 }
 
 @media (min-width: 640px) {
-  .collection-filter-pills {
-    gap: 0.5rem;
-  }
-
-  .collection-filter-pill {
-    padding: 0.5rem 1rem;
-    font-size: 0.875rem;
-  }
-
   /* Desktop always wraps — no scroll needed */
   .collection-filters.is-scrollable {
     overflow-x: visible;