fix: video not rendering — add TipTap Video extension, allow HTTP src

TipTap didn't recognize <video> tags without a custom node extension,
serializing them as escaped text. Also revert video src to allow HTTP
since request.base_url returns http:// behind reverse proxy.

src/lib/tiptap-video.ts

@@ -0,0 +1,30 @@
+import { Node, mergeAttributes } from '@tiptap/core';
+
+/**
+ * TipTap extension for inline <video> elements.
+ *
+ * Without this extension, TipTap does not recognize <video> tags and
+ * serializes them as escaped text when calling editor.getHTML().
+ */
+export const VideoExtension = Node.create({
+  name: 'video',
+  group: 'block',
+  atom: true,
+
+  addAttributes() {
+    return {
+      src: { default: null },
+      controls: { default: true },
+      class: { default: null },
+      preload: { default: 'metadata' },
+    };
+  },
+
+  parseHTML() {
+    return [{ tag: 'video' }];
+  },
+
+  renderHTML({ HTMLAttributes }) {
+    return ['video', mergeAttributes(HTMLAttributes, { controls: '' })];
+  },
+});