feat: category tags (design/film/photo/text) on the portfolio index

new categories taxonomy, multi-value per project. shown inline in each ls row as [tag] after the slug, muted like the other row metadata and inverting with it on hover/select. reuses the existing shared taxonomy template, so /categories/ and /categories/<tag>/ come for free as browsable archives in the same shell style already used for schools/degrees/semesters.\n\nassigned by medium: design for anything with plans/models, film for the two video projects, photo for the trieste study trip, text alongside design for translation (collage + accompanying theoretical text).

layouts/portfolio/list.html

@@ -16,7 +16,7 @@
            data-img="{{ with $p.Params.thumbnail }}{{ . | relURL }}{{ end }}"
            data-name="{{ $p.Slug }}"
            {{ if eq $i 0 }}class="is-selected"{{ end }}>
-      <span class="tui__perm">drwxr-xr-x</span><span class="tui__date">{{ $p.Date.Format "2006" }}</span><span class="tui__name">{{ $p.Slug }}/</span>
+      <span class="tui__perm">drwxr-xr-x</span><span class="tui__date">{{ $p.Date.Format "2006" }}</span><span class="tui__name">{{ $p.Slug }}/{{ with $p.Params.categories }} <span class="tui__tags">{{ range . }}[{{ . }}]{{ end }}</span>{{ end }}</span>
     </a></li>
     {{ end }}
   </ul>