chore(infra): port 9000, make help, db skip-check, Vite CSS fix

- Django dev server now runs on :9000 (was :8000)
- `make` without args shows all targets with descriptions
- `make db` skips docker start if :5432 already reachable (nc check)
- `make seed` and `make superuser` added as explicit targets
- vite.config.js: assetFileNames without hash so static/dist/main.css
  matches the {% static 'dist/main.css' %} reference in base.html
  (run `npm run build` once after checkout to regenerate the CSS file)

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

vite.config.js

@@ -8,6 +8,9 @@ export default defineConfig({
     emptyOutDir: true,
     rollupOptions: {
       input: 'static/src/main.css',
+      output: {
+        assetFileNames: '[name][extname]',
+      },
     },
   },
 })