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/base.html

@@ -4,6 +4,7 @@
     <meta charset="utf-8">
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <title>{% block title %}PI Weekly{% endblock %} — Plymouth Independent</title>
+    <link rel="icon" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'><text y='.9em' font-size='90'>📰</text></svg>">
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@picocss/pico@2/css/pico.min.css">
     <link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">
 </head>
@@ -36,6 +37,48 @@
     <footer class="container">
         <small>PI Weekly Newspaper Generator</small>
     </footer>
+    <dialog id="confirm-dialog">
+        <article>
+            <header>
+                <button aria-label="Close" rel="prev" onclick="closeConfirm()"></button>
+                <p><strong id="confirm-title">Confirm</strong></p>
+            </header>
+            <p id="confirm-message"></p>
+            <footer>
+                <button class="secondary" onclick="closeConfirm()">Cancel</button>
+                <button id="confirm-ok" onclick="submitConfirm()">Confirm</button>
+            </footer>
+        </article>
+    </dialog>
+    <script>
+    let _confirmTarget = null;
+    function confirmAction(message, formOrEl, title) {
+        _confirmTarget = formOrEl;
+        document.getElementById('confirm-title').textContent = title || 'Confirm';
+        document.getElementById('confirm-message').textContent = message;
+        const btn = document.getElementById('confirm-ok');
+        btn.className = '';
+        if (formOrEl.dataset.confirmDanger) {
+            btn.className = 'btn-danger-fill';
+        }
+        const dialog = document.getElementById('confirm-dialog');
+        document.documentElement.classList.add('modal-is-open', 'modal-is-opening');
+        dialog.showModal();
+        setTimeout(() => document.documentElement.classList.remove('modal-is-opening'), 200);
+    }
+    function closeConfirm() {
+        const dialog = document.getElementById('confirm-dialog');
+        document.documentElement.classList.add('modal-is-closing');
+        setTimeout(() => {
+            dialog.close();
+            document.documentElement.classList.remove('modal-is-open', 'modal-is-closing');
+            _confirmTarget = null;
+        }, 200);
+    }
+    function submitConfirm() {
+        if (_confirmTarget) _confirmTarget.submit();
+    }
+    </script>
     {% block scripts %}{% endblock %}
 </body>
 </html>