feat(admin): add bulk song selection with playlist assignment

- Introduces bulk checkboxes on the songs list page to select multiple songs
- Adds a toolbar with dropdown to add selected songs to existing playlists or create a new playlist
- Implements `/songs/bulk-add` POST endpoint for efficient batch addition of tracks to playlists
- Auto-upgrades playlist visibility when adding more-restrictive songs
- Supports preselecting songs via query parameter when creating a new playlist (`?songs=1,2,3`)
- Includes custom-styled checkboxes, toast notifications, and keyboard-friendly UI interactions

public/js/navigate.js

@@ -9,11 +9,24 @@
     catch { return false; }
   }
 
+  // Re-execute script tags injected via innerHTML (browser skips them otherwise).
+  function runScripts(container) {
+    container.querySelectorAll('script').forEach((old) => {
+      const s = document.createElement('script');
+      [...old.attributes].forEach((a) => s.setAttribute(a.name, a.value));
+      s.textContent = old.textContent;
+      old.replaceWith(s);
+    });
+  }
+
   // Swap #page-shell content, update title, and optionally push history.
   function applyPage(doc, finalUrl, pushState) {
     const newShell = doc.getElementById('page-shell');
     const curShell = document.getElementById('page-shell');
-    if (newShell && curShell) curShell.innerHTML = newShell.innerHTML;
+    if (newShell && curShell) {
+      curShell.innerHTML = newShell.innerHTML;
+      runScripts(curShell);
+    }
     document.title = doc.title;
     if (pushState) history.pushState({ btiNav: true }, doc.title, finalUrl);
     window.scrollTo(0, 0);

src/views/mymusic/playlist_form.ejs

@@ -138,7 +138,7 @@
     const form = document.getElementById('reorder-form');
     document.getElementById('reorder-order').value =
       [...list.querySelectorAll('li')].map(li => li.dataset.songId).join(',');
-    fetch(form.action, { method: 'POST', body: new FormData(form) })
+    fetch(form.action, { method: 'POST', body: new URLSearchParams(new FormData(form)) })
       .catch(err => console.error('[reorder] failed:', err));
   });