ShareLinks: make guest redemption actually work end to end

The sign-in bootstrap sent the auth request body as a JS object, so it
was coerced to [object Object] and AuthenticateByName returned 400. Send
JSON.stringify(...) instead.

Guest credentials were written to localStorage as a flat object under
made-up keys. jellyfin-web reads jellyfin_credentials as
{Servers:[{Id,AccessToken,UserId,...}]}, so the guest was treated as
logged out. Write that shape, pulling server Id/name from
System/Info/Public, and redirect with the 10.11 hash route
(#/details?id=...&serverId=...) instead of the legacy #!/ form that
rendered a blank page.

Creating a link now rejects folders and libraries (only movies and
episodes are shareable) so a guest cannot land on an empty tag-filtered
library. Item ids from the menu action are validated as GUIDs client
side, rejected creates are logged server side, malformed redeem tokens
return 404 instead of 500, and the admin table shows the item name and a
copyable link instead of the raw item id.

Jellyfin.Plugin.ShareLinks/Web/configPage.html

@@ -170,6 +170,7 @@
                                 <tr>
                                     <th style="width: 9rem;">Status</th>
                                     <th>Item</th>
+                                    <th style="width: 14rem;">Link</th>
                                     <th style="width: 11rem;">Guest</th>
                                     <th style="width: 11rem;">Expires</th>
                                     <th style="width: 9rem;" class="sl-right">Actions</th>
@@ -177,7 +178,7 @@
                             </thead>
                             <tbody id="LinksBody">
                                 <tr>
-                                    <td colspan="5" class="sl-muted">No links loaded yet.</td>
+                                    <td colspan="6" class="sl-muted">No links loaded yet.</td>
                                 </tr>
                             </tbody>
                         </table>
@@ -237,7 +238,7 @@
                 }) : [];
 
                 if (!items.length) {
-                    body.innerHTML = '<tr><td colspan="5" class="sl-muted">No active links.</td></tr>';
+                    body.innerHTML = '<tr><td colspan="6" class="sl-muted">No active links.</td></tr>';
                     page.querySelector('#LinksStatus').textContent = 'No share links.';
                     return;
                 }
@@ -247,13 +248,18 @@
                     var itemName = escapeHtml(record.ItemNameSnapshot || record.ItemId || '');
                     var guestName = escapeHtml(record.GuestUserName || 'n/a');
                     var expires = fmtDate(record.ExpiresAtUtc || record.ExpiresAt);
+                    var shareUrl = record.ShareUrl ? escapeHtml(record.ShareUrl) : '';
+                    var linkCell = shareUrl
+                        ? '<button is="emby-button" type="button" class="raised" data-copy="' + shareUrl + '"><span>Copy</span></button> ' +
+                          '<a href="' + shareUrl + '" target="_blank" rel="noopener">Open</a>'
+                        : '<span class="sl-muted">n/a</span>';
                     return [
                         '<tr>',
                         '<td>', escapeHtml(status), '</td>',
                         '<td>',
                         '<div><strong>', itemName, '</strong></div>',
-                        '<div class="sl-muted">', escapeHtml(record.ItemId || ''), '</div>',
                         '</td>',
+                        '<td>', linkCell, '</td>',
                         '<td>', guestName, '</td>',
                         '<td>', escapeHtml(expires), '</td>',
                         '<td class="sl-right">',
@@ -271,6 +277,12 @@
                     });
                 });
 
+                Array.from(body.querySelectorAll('button[data-copy]')).forEach(function (button) {
+                    button.addEventListener('click', function () {
+                        copyShareUrl(button);
+                    });
+                });
+
                 page.querySelector('#LinksStatus').textContent = items.length + ' link' + (items.length === 1 ? '' : 's') + ' loaded.';
             }
 
@@ -285,10 +297,57 @@
                     renderLinks(list || []);
                 }).catch(function (error) {
                     status.textContent = 'Could not load share links.';
-                    page.querySelector('#LinksBody').innerHTML = '<tr><td colspan="5" class="sl-muted">' + escapeHtml(error && error.message ? error.message : 'Load failed.') + '</td></tr>';
+                    page.querySelector('#LinksBody').innerHTML = '<tr><td colspan="6" class="sl-muted">' + escapeHtml(error && error.message ? error.message : 'Load failed.') + '</td></tr>';
                 });
             }
 
+            function copyShareUrl(button) {
+                var url = button.getAttribute('data-copy');
+                if (!url) {
+                    return;
+                }
+
+                copyText(url).then(function () {
+                    var span = button.querySelector('span');
+                    if (!span) {
+                        return;
+                    }
+                    span.textContent = 'Copied';
+                    window.setTimeout(function () {
+                        span.textContent = 'Copy';
+                    }, 2000);
+                });
+            }
+
+            function copyText(text) {
+                if (navigator.clipboard && navigator.clipboard.writeText) {
+                    return navigator.clipboard.writeText(text).catch(function () {
+                        return fallbackCopyText(text);
+                    });
+                }
+
+                return fallbackCopyText(text);
+            }
+
+            function fallbackCopyText(text) {
+                var textarea = document.createElement('textarea');
+                textarea.value = text;
+                textarea.setAttribute('readonly', 'readonly');
+                textarea.style.position = 'fixed';
+                textarea.style.top = '-1000px';
+                textarea.style.left = '-1000px';
+                document.body.appendChild(textarea);
+                textarea.focus();
+                textarea.select();
+                try {
+                    document.execCommand('copy');
+                } catch (error) {
+                    // Best effort only.
+                }
+                textarea.remove();
+                return Promise.resolve();
+            }
+
             function revokeLink(id) {
                 if (!id) {
                     return;