feat(REQ-001): add portfolio comment history API, CLI, repository, migration, and tests

Agent-Logs-Url: https://github.com/genichin/portfolio-hub/sessions/64fc2cec-78f5-41d1-99a4-45f868781edd

Co-authored-by: genichin <4282227+genichin@users.noreply.github.com>

app/schemas/portfolio.py

@@ -123,6 +123,22 @@ class ResetPortfolioRequest(BaseModel):
     infer_symbol: str | None = None
 
 
+class CommentCreateRequest(BaseModel):
+    content: str
+
+
+class CommentUpdateRequest(BaseModel):
+    content: str
+
+
+class CommentResponse(BaseModel):
+    id: str
+    portfolio_id: str
+    content: str
+    created_at: datetime | None = None
+    updated_at: datetime | None = None
+
+
 class ErrorResponse(BaseModel):
     detail: str
     model_config = ConfigDict(extra="ignore")