feat: add forwarding & reply detection with frontend indicators

- Enhanced messageMetadata to capture referenced message content
- Added reply indicator (↩️ Replying to @username + content snippet)
- Added forward badge (🔁 Forwarded) and crosspost badge (📢 Crossposted)
- Frontend auto-fetches referenced message content when metadata is empty
- Added getMessageById API helper

services/frontend/src/shared/api/client.ts

@@ -166,6 +166,12 @@ export function reanalyzeMessage(id: string): Promise<void> {
   return request<void>(`/api/messages/${id}/reanalyze`, { method: "POST" });
 }
 
+export function getMessageById(
+  id: string,
+): Promise<MessageRecord | null> {
+  return request<MessageRecord | null>(`/api/messages/detail/${id}`);
+}
+
 export function reanalyzeErrorBatch(opts: {
   guildId?: string;
   channelId?: string;

services/frontend/src/shared/lib/utils.ts

@@ -27,6 +27,16 @@ export interface MessageMetadata {
     threadId?: string;
     threadName?: string;
   };
+  reference?: {
+    messageId: string | null;
+    channelId: string | null;
+    guildId: string | null;
+    type: string | null;
+    content: string | null;
+    repliedUsername: string | null;
+    repliedUserId: string | null;
+  } | null;
+  isCrosspost?: boolean;
 }
 
 export function parseMetadata(value: string | null): MessageMetadata {