feat: multimodal video detection + reply/forward/crosspost + batch optimization

- Video frame extraction via ffmpeg (4 key frames per video → vision LLM)
- Video display in FE MessageCard with HTML5 <video> player
- Reply/forward/crosspost indicator in FE + pipeline in DG/BE
- Fix: missing sanitizeAiContent + escapeXml in media path (prompt injection)
- Optimize: text-only batch results saved to DB immediately, no longer wait for media analysis
- BE mapper/schema/repo: add reference fields (is_reply, is_forward, etc.)

services/backend/src/modules/messages/messages.repository.ts

@@ -134,6 +134,12 @@ export class MessagesRepository {
         type: data.type ?? "text",
         metadata: null,
         ai_status: "pending",
+        is_reply: data.isReply ?? false,
+        is_forward: data.isForward ?? false,
+        is_crosspost: data.isCrosspost ?? false,
+        reference_message_id: data.referenceMessageId ?? null,
+        reference_channel_id: data.referenceChannelId ?? null,
+        reference_guild_id: data.referenceGuildId ?? null,
       })
       .returning();
 
@@ -260,6 +266,12 @@ export class MessagesRepository {
         ai_severity: pgMessagesTable.ai_severity,
         ai_confidence: pgMessagesTable.ai_confidence,
         ai_analysis: pgMessagesTable.ai_analysis,
+        is_reply: pgMessagesTable.is_reply,
+        is_forward: pgMessagesTable.is_forward,
+        is_crosspost: pgMessagesTable.is_crosspost,
+        reference_message_id: pgMessagesTable.reference_message_id,
+        reference_channel_id: pgMessagesTable.reference_channel_id,
+        reference_guild_id: pgMessagesTable.reference_guild_id,
       })
       .from(pgMessagesTable)
       .where(and(...conditions))

services/backend/src/modules/messages/messages.schema.ts

@@ -19,6 +19,12 @@ export const messageCreateSchema = z.object({
   avatarUrl: z.string().optional(),
   content: z.string(),
   type: z.enum(["text", "edited", "deleted"]).default("text"),
+  isReply: z.boolean().optional(),
+  isForward: z.boolean().optional(),
+  isCrosspost: z.boolean().optional(),
+  referenceMessageId: z.string().optional(),
+  referenceChannelId: z.string().optional(),
+  referenceGuildId: z.string().optional(),
 });
 
 export const messageUpdateSchema = z.object({