feat(groups): optional forge source label in message footers

- Group.forgeLabel (default off, editable per group in the console) shows the
  source forge on every message the group's routes dispatch
- Discord embed footer: forge name next to the repo + the site's favicon as
  icon_url (Gitea instance's own favicon from its origin)
- Telegram footer: hyperlinked site name (GitHub or Gitea hostname); custom
  webhooks render a plain 'Custom' label
- forgeInfo() derives branding from event.provider + repository.html_url;
  dispatch attaches it to the NeutralMessage like mentionRoleIds
- validateGroups accepts forgeLabel booleans; GroupEditor gains the toggle
- tests: forgeInfo unit, discord/telegram footer render, dispatch on/off
- docs: groups.md + message-format.md (en/zh), config.example.yaml, AGENTS.md
- fix: wrangler.jsonc compatibility_date was an incomplete '2026-'

server/lib/drivers/discord/render.ts

@@ -39,6 +39,10 @@ export function renderNeutralMessage(message: NeutralMessage): FormattedMessage
 
   // Safety net: clamp every embed part to the Discord API limits so a single
   // oversized formatter or custom payload can never hard-fail the request.
+  const footerText = cap(
+    [message.forge?.name, message.footer].filter(Boolean).join(" · "),
+    MAX_FOOTER,
+  );
   return {
     content,
     embeds: [
@@ -61,7 +65,9 @@ export function renderNeutralMessage(message: NeutralMessage): FormattedMessage
             value: cap(f.value, MAX_FIELD_VALUE),
             inline: f.inline,
           })),
-        footer: message.footer ? { text: cap(message.footer, MAX_FOOTER) } : undefined,
+        footer: footerText
+          ? { text: footerText, icon_url: message.forge?.iconUrl }
+          : undefined,
         timestamp: message.timestamp,
       },
     ],