feat(media): implement caching for chat media and update components to use cached media

src/stores/chat/chat-machine.actors.ts

@@ -156,6 +156,7 @@ async function sendMessageViaHttp(content: string): Promise<{
     log.error("[chat-machine] sendMessageHttpActor failed", { error: result.error });
     throw result.error;
   }
+  void chatRepo.prefetchMediaForSendResponse(result.data);
   const isMessageLimit =
     result.data.lockDetail.locked &&
     result.data.lockDetail.showUpgrade &&

src/stores/chat/chat-machine.helpers.ts

@@ -356,6 +356,7 @@ export async function readAndSyncHistory(): Promise<{
   log.debug("[chat-machine] loadHistory NETWORK DONE", {
     count: networkUi.length,
   });
+  void chatRepo.prefetchMediaForMessages(networkResult.data.messages);
 
   // 3. 用 network 覆盖 local
   const saveResult = await chatRepo.saveMessagesToLocal(networkResult.data.messages);