fix: delete issues, ePub reader (JSZip, linear cover, fonts), Pico dialog, UI polish

- Add POST /issues/<id>/delete route with file cleanup
- Fix ePub reader: add JSZip dependency, make cover linear in spine,
  inject system fonts into rendition
- Replace browser confirm() with Pico CSS dialog component
- Fix dashboard button sizing and consistency
- Add favicon, override Pico font stack to suppress Firefox warnings
- Compact issue action buttons

Made-with: Cursor

templates/dashboard.html

@@ -34,7 +34,7 @@
         <button type="submit">Fetch Now</button>
     </form>
     <a href="/articles" role="button" class="outline">View</a>
-    <a href="/publish" role="button">Publish New</a>
+    <a href="/publish" role="button" class="outline">Publish New</a>
 </div>
 
 {% if latest_issue %}