feat: warn on magnet-only uploads and make video fetch limit configurable

- Add a confirmation dialog in `UploadModal.js` when a user uploads a video with only a magnet link to warn about potential data loss.
- Replace the hardcoded limit of 300 in `NostrClient.fetchVideos` with a configurable limit that respects `DEFAULT_VIDEO_REQUEST_LIMIT` and `MAX_VIDEO_REQUEST_LIMIT`, improving client-side scalability.

js/nostr/client.js

@@ -5856,11 +5856,14 @@ export class NostrClient {
   /**
    * fetchVideos => old approach
    */
-  async fetchVideos() {
+  async fetchVideos(options = {}) {
+    const requestedLimit = Number(options?.limit);
+    const resolvedLimit = this.clampVideoRequestLimit(requestedLimit, DEFAULT_VIDEO_REQUEST_LIMIT);
+
     const filter = {
       kinds: [30078],
       "#t": ["video"],
-      limit: 300,
+      limit: resolvedLimit,
       since: 0,
     };
 

js/ui/components/UploadModal.js

@@ -744,6 +744,20 @@ export class UploadModal {
       );
     }
 
+    const hasDirectUrl = typeof rawPayload.url === "string" && rawPayload.url.trim().length > 0;
+    const hasMagnet = typeof rawPayload.magnet === "string" && rawPayload.magnet.trim().length > 0;
+
+    if (!hasDirectUrl && hasMagnet) {
+      const confirmed = typeof window !== "undefined" && window.confirm
+        ? window.confirm("You are uploading with a magnet link only.\n\nSince this video is not hosted on a server, it will only be playable as long as you (or others) continue seeding it.\n\nDo you want to proceed?")
+        : true;
+
+      if (!confirmed) {
+        this.updateCustomSubmitButtonState();
+        return;
+      }
+    }
+
     const nip71Metadata = this.nip71FormManager.collectSection("custom");
     if (nip71Metadata) {
       rawPayload.nip71 = nip71Metadata;