feat: Implement recent chats feature with API endpoint and UI integration

app/models.py

@@ -103,3 +103,12 @@ class StatusResponse(BaseModel):
     session_active: bool
     phone_number: Optional[str]
     code_sent: bool = False
+
+
+class RecentChat(BaseModel):
+    chat_id: str
+    display_name: str
+    chat_type: str
+    username: Optional[str] = None
+    phone_number: Optional[str] = None
+    last_used_at: Optional[datetime] = None