feat: replace server-rendered index with JS-rendered shell page

- Rewrites indexPage to render a shell page with embedded JSON + JS
- Adds searchJs with vanilla JS for client-side list rendering, filtering, sorting
- Hash-based sort modes (#alpha, #tags, #course)
- Search filters by title and filename (case-insensitive)
- Fix: recipe links use /recipes/ prefix and encodeURIComponent for # encoding
- Fix: avoid double-render on initial page load

src/Roux/Html.hs

@@ -255,7 +255,7 @@ searchJs = T.unlines
     , "  if (items.length === 0) return '<p>No recipes found.</p>';"
     , "  let html = '<ul class=\'roux-recipes\'>';"
     , "  items.forEach(r => {"
-    , "    html += '<li><a href=\"' + encodeURI(r.filename) + '\">' + escapeHtml(r.title) + '</a></li>';"
+    , "    html += '<li><a href=\"/recipes/' + encodeURIComponent(r.filename) + '\">' + escapeHtml(r.title) + '</a></li>';"
     , "  });"
     , "  html += '</ul>';"
     , "  return html;"
@@ -317,10 +317,9 @@ searchJs = T.unlines
     , "}"
     , "window.addEventListener('hashchange', updateActiveNav);"
     , ""
-    , "// Initial render"
+    , "// Initial render -- setting hash triggers hashchange"
     , "if (!location.hash) location.hash = 'alpha';"
-    , "updateActiveNav();"
+    , "else { updateActiveNav(); render(); }"
-    , "render();"
     , ""
     , "})();"
     ]