Refactor video modal sharing options into a unified Share menu

- Replaced the standalone "Copy Magnet" button and "Share" button with a new Share menu.
- Implemented `createVideoShareMenuPanel` to render the new menu with "Copy URL", "Share on Nostr", "Copy Magnet", and "Copy CDN Link" options.
- Updated `VideoModal.js` to manage the share menu state and handle actions.
- Added `video:share-nostr` and `video:copy-cdn` event handlers in `app.js`.
- Removed the `#copyMagnetBtn` element from `video-modal.html`.
- Preserved existing functionality for "Copy URL" and "Copy Magnet".
- "Share on Nostr" is currently a placeholder logging a message, disabled for logged-out users.
- "Copy CDN Link" is disabled if no URL is available.

js/app.js

@@ -8459,7 +8459,7 @@ class Application {
       this.currentVideo.torrentSupported = !!magnetForPlayback;
     }
     this.currentMagnetUri = magnetForPlayback || null;
-    this.setCopyMagnetState(!!magnetForPlayback);
+    // this.setCopyMagnetState(!!magnetForPlayback); // Removed
 
     const unsubscribers = [];
     const subscribe = (eventName, handler) => {
@@ -8757,8 +8757,8 @@ class Application {
 
     this.currentMagnetUri = sanitizedMagnet || null;
 
-    this.setCopyMagnetState(!!sanitizedMagnet);
-    this.setShareButtonState(true);
+    // this.setCopyMagnetState(!!sanitizedMagnet); // Removed
+    // this.setShareButtonState(true); // Moved to after showModalWithPoster
 
     const nevent = window.NostrTools.nip19.neventEncode({ id: eventId });
     const pushUrl =
@@ -8781,6 +8781,8 @@ class Application {
 
     await this.showModalWithPoster(this.currentVideo);
 
+    this.setShareButtonState(true);
+
     this.commentController?.load(this.currentVideo);
 
     const playbackOptions = {
@@ -9131,8 +9133,8 @@ class Application {
 
     this.currentMagnetUri = sanitizedMagnet || null;
 
-    this.setCopyMagnetState(!!sanitizedMagnet);
-    this.setShareButtonState(false);
+    // this.setCopyMagnetState(!!sanitizedMagnet);
+    // this.setShareButtonState(false);
 
     if (this.videoModal) {
       this.videoModal.updateMetadata({
@@ -9150,6 +9152,8 @@ class Application {
 
     await this.showModalWithPoster(this.currentVideo, hasTrigger ? { trigger } : {});
 
+    this.setShareButtonState(false);
+
     this.commentController?.load(null);
 
     const shareUrl = this.buildShareUrlFromEventId(this.currentVideo.id);