fix: include blog models in Tailwind content scan for tag colours

Tag colour classes (bg-cyan-100, text-cyan-900, etc.) are generated
dynamically in TagMetadata.get_css_classes() in apps/blog/models.py.
Tailwind's content scanner only covered HTML templates, so these classes
were purged from the CSS build — rendering tags as white-on-white.

Add apps/blog/models.py to the Tailwind content array so the JIT
compiler detects and retains the dynamic colour classes.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

theme/static_src/tailwind.config.js

@@ -3,6 +3,7 @@ module.exports = {
   content: [
     "../../templates/**/*.html",
     "../../apps/**/templates/**/*.html",
+    "../../apps/blog/models.py",
   ],
   theme: {
     extend: {