feat：新增大屏存取发布接口

app/services/conversation.py

@@ -21,7 +21,7 @@ def make_title(prompt: str) -> str:
 class ConversationStore(Protocol):
     """内存和 MongoDB 实现同一组方法，业务代码不需要关心具体存储"""
 
-    async def create(self, user_id: int) -> str: ...
+    async def create(self, user_id: int, screen_id: str | None = None) -> str: ...
 
     async def exists(self, conversation_id: str, user_id: int) -> bool:
         """会话已签发、未过期且属于该用户；不属于时与不存在同样返回 False"""
@@ -34,9 +34,21 @@ class ConversationStore(Protocol):
     async def save_turn(self, turn: Turn) -> None: ...
 
     async def list_by_user(
-        self, user_id: int, limit: int, offset: int
+        self, user_id: int, limit: int, offset: int, screen_id: str | None = None
     ) -> list[ConversationSummary]:
-        """该用户已产生对话的会话，按最近更新时间倒序；没有对话的空会话不返回"""
+        """该用户已产生对话的会话，按最近更新时间倒序；没有对话的空会话不返回；给了 screen_id 只返回该大屏的"""
+        ...
+
+    async def count_by_user(self, user_id: int, screen_id: str | None = None) -> int:
+        """与 list_by_user 同一口径的总数"""
+        ...
+
+    async def rename(self, conversation_id: str, user_id: int, title: str) -> bool:
+        """会话不存在或不属于该用户返回 False"""
+        ...
+
+    async def delete(self, conversation_id: str, user_id: int) -> bool:
+        """连同对话轮次一起删除；会话不存在或不属于该用户返回 False"""
         ...
 
 
@@ -51,6 +63,8 @@ class InMemoryConversationStore:
         # 会话 ID -> 创建时间；轮次按 thread_id 去重并保持首次写入顺序
         self._created: dict[str, datetime] = {}
         self._owner: dict[str, int] = {}
+        self._screen: dict[str, str | None] = {}
+        self._titles: dict[str, str] = {}
         self._turns: dict[str, dict[str, Turn]] = {}
 
     def _purge_expired(self) -> None:
@@ -61,15 +75,18 @@ class InMemoryConversationStore:
             for key, created in self._created.items()
             if created < deadline and not self._turns.get(key)
         ]:
-            del self._created[conversation_id]
-            self._owner.pop(conversation_id, None)
-            self._turns.pop(conversation_id, None)
+            self._forget(conversation_id)
 
-    async def create(self, user_id: int) -> str:
+    def _forget(self, conversation_id: str) -> None:
+        for table in (self._created, self._owner, self._screen, self._titles, self._turns):
+            table.pop(conversation_id, None)
+
+    async def create(self, user_id: int, screen_id: str | None = None) -> str:
         self._purge_expired()
         conversation_id = str(uuid4())
         self._created[conversation_id] = _now()
         self._owner[conversation_id] = user_id
+        self._screen[conversation_id] = screen_id
         return conversation_id
 
     async def exists(self, conversation_id: str, user_id: int) -> bool:
@@ -94,8 +111,8 @@ class InMemoryConversationStore:
             turn = turn.model_copy(update={"created_at": existing.created_at})
         self._turns[turn.conversation_id][turn.thread_id] = turn
 
-    async def list_by_user(
-        self, user_id: int, limit: int, offset: int
+    def _summaries(
+        self, user_id: int, screen_id: str | None
     ) -> list[ConversationSummary]:
         summaries = []
         for conversation_id, owner in self._owner.items():
@@ -105,14 +122,37 @@ class InMemoryConversationStore:
             )
             if owner != user_id or not turns:
                 continue
+            if screen_id is not None and self._screen.get(conversation_id) != screen_id:
+                continue
             summaries.append(
                 ConversationSummary(
                     conversation_id=conversation_id,
-                    title=make_title(turns[0].prompt),
+                    title=self._titles.get(conversation_id) or make_title(turns[0].prompt),
+                    screen_id=self._screen.get(conversation_id),
                     updated_at=turns[-1].created_at,
                 )
             )
         summaries.sort(
             key=lambda item: (item.updated_at, item.conversation_id), reverse=True
         )
-        return summaries[offset : offset + limit]
+        return summaries
+
+    async def list_by_user(
+        self, user_id: int, limit: int, offset: int, screen_id: str | None = None
+    ) -> list[ConversationSummary]:
+        return self._summaries(user_id, screen_id)[offset : offset + limit]
+
+    async def count_by_user(self, user_id: int, screen_id: str | None = None) -> int:
+        return len(self._summaries(user_id, screen_id))
+
+    async def rename(self, conversation_id: str, user_id: int, title: str) -> bool:
+        if not await self.exists(conversation_id, user_id):
+            return False
+        self._titles[conversation_id] = title
+        return True
+
+    async def delete(self, conversation_id: str, user_id: int) -> bool:
+        if not await self.exists(conversation_id, user_id):
+            return False
+        self._forget(conversation_id)
+        return True