feat(models): add series column to Topic for content columns

Topic model: new series VARCHAR field (optional, indexed)
Schema: series in TopicBase/TopicCreate/TopicUpdate
API: GET /api/topics supports ?series= query param
DB migration: ALTER TABLE topics ADD COLUMN series

Ultraworked with Sisyphus

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

platform/backend/app/schemas.py

@@ -76,6 +76,7 @@ class TopicBase(BaseModel):
     scoring_data: Dict[str, Any] = {}
     lock_by: Optional[str] = None
     lock_at: Optional[datetime] = None
+    series: Optional[str] = None
 
 
 class TopicCreate(BaseModel):
@@ -90,6 +91,7 @@ class TopicCreate(BaseModel):
     tags: List[str] = []
     custom_data: Dict[str, Any] = {}
     scoring_data: Dict[str, Any] = {}
+    series: Optional[str] = None
 
 
 class TopicAnalyzeRequest(BaseModel):
@@ -123,6 +125,7 @@ class TopicUpdate(BaseModel):
     scoring_data: Optional[Dict[str, Any]] = None
     priority_score: Optional[int] = None
     total_score: Optional[float] = None
+    series: Optional[str] = None
 
 
 class TopicResponse(TopicBase):