feat: add board goal schemas and validation

backend/app/schemas/boards.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 from datetime import datetime
 from uuid import UUID
 
+from pydantic import model_validator
 from sqlmodel import SQLModel
 
 
@@ -10,16 +11,33 @@ class BoardBase(SQLModel):
     name: str
     slug: str
     gateway_id: UUID | None = None
+    board_type: str = "goal"
+    objective: str | None = None
+    success_metrics: dict[str, object] | None = None
+    target_date: datetime | None = None
+    goal_confirmed: bool = False
+    goal_source: str | None = None
 
 
 class BoardCreate(BoardBase):
-    pass
+    @model_validator(mode="after")
+    def validate_goal_fields(self):
+        if self.board_type == "goal":
+            if not self.objective or not self.success_metrics:
+                raise ValueError("Goal boards require objective and success_metrics")
+        return self
 
 
 class BoardUpdate(SQLModel):
     name: str | None = None
     slug: str | None = None
     gateway_id: UUID | None = None
+    board_type: str | None = None
+    objective: str | None = None
+    success_metrics: dict[str, object] | None = None
+    target_date: datetime | None = None
+    goal_confirmed: bool | None = None
+    goal_source: str | None = None
 
 
 class BoardRead(BoardBase):