Add video picker and Discord video attachments.

The picker accepts one MP4 or WebM, the thread lightbox zooms photos, and Discord gets the video as a file on a follow-up message so photo embeds still render.

internal/events/event.go

@@ -1,14 +1,27 @@
 package events
 
 import (
+	"io"
 	"net/url"
 	"strings"
 )
 
-// Image is a public photo already attached to a site post.
+// Image is a public photo or video already attached to a site post.
 type Image struct {
 	URL         string
 	Description string
+	Kind        string
+}
+
+// Media is a local upload still held from the create request so Discord can
+// attach the bytes. Photos carry re-encoded Bytes; videos carry an open Body.
+type Media struct {
+	Name        string
+	ContentType string
+	Kind        string
+	Size        int64
+	Body        io.ReadCloser
+	Bytes       []byte
 }
 
 // PostEvent is a Discord-free snapshot of a site post after a successful write.
@@ -29,6 +42,8 @@ type PostEvent struct {
 // PostCreated is emitted after a successful site create.
 type PostCreated struct {
 	PostEvent
+	Media   []Media `json:"-"`
+	Release func()  `json:"-"`
 }
 
 // PostUpdated is emitted after a successful site edit.
@@ -36,6 +51,13 @@ type PostUpdated struct {
 	PostEvent
 }
 
+// PostedToDiscord is emitted after the Discord subscriber finishes with a
+// PostCreated (sent, skipped, or failed). Release deletes held upload files.
+type PostedToDiscord struct {
+	PostID  string
+	Release func() `json:"-"`
+}
+
 // Permalink builds /questions/{root}#post-{id}, prefixed by baseURL when set.
 func Permalink(baseURL, rootID, postID string) string {
 	path := "/questions/" + url.PathEscape(rootID) + "#post-" + url.PathEscape(postID)