feat: add cumulative checkin tracking mode for goals

Goals can now choose between milestone-based progress (existing) and
cumulative checkin-based progress (new). Cumulative mode supports
cross-unit conversion (e.g. kcal → g fat) via a configurable
conversion rate. New GoalCheckin model stores daily inputs; progress
auto-recalculates on every checkin C/U/D. Backup import/export covers
the new table. Frontend GoalDialog, GoalDetailPage and GoalPage cards
adapt to show cumulative progress or milestone progress based on
track_type.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

api/app/schemas/goal.py

@@ -6,6 +6,37 @@ from app.schemas.category import CategoryResponse
 from app.schemas.task import TaskResponse
 
 
+# ============ GoalCheckin Schemas ============
+
+class GoalCheckinCreate(BaseModel):
+    value: float = Field(..., gt=0)
+    note: Optional[str] = None
+    checkin_date: date
+
+
+class GoalCheckinUpdate(BaseModel):
+    value: Optional[float] = Field(None, gt=0)
+    note: Optional[str] = None
+    checkin_date: Optional[date] = None
+
+    @property
+    def clearable_fields(self) -> set:
+        return {"note"}
+
+
+class GoalCheckinResponse(BaseModel):
+    id: int
+    uuid: Optional[str] = None
+    goal_id: int
+    value: float
+    note: Optional[str] = None
+    checkin_date: date
+    created_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
 # ============ GoalStep Schemas ============
 
 class GoalStepBase(BaseModel):
@@ -71,6 +102,11 @@ class GoalBase(BaseModel):
     title: str = Field(..., max_length=200)
     description: Optional[str] = None
     status: str = Field(default="active", pattern="^(active|paused|completed|abandoned)$")
+    track_type: str = Field(default="milestone", pattern="^(milestone|cumulative)$")
+    target_value: Optional[float] = None
+    target_unit: Optional[str] = Field(None, max_length=20)
+    input_unit: Optional[str] = Field(None, max_length=20)
+    conversion_rate: float = Field(default=1.0)
     target_date: Optional[date] = None
     category_id: Optional[int] = None
     color: str = Field(default="#FFB7C5", max_length=20)
@@ -86,6 +122,11 @@ class GoalUpdate(BaseModel):
     title: Optional[str] = Field(None, max_length=200)
     description: Optional[str] = None
     status: Optional[str] = Field(None, pattern="^(active|paused|completed|abandoned)$")
+    track_type: Optional[str] = Field(None, pattern="^(milestone|cumulative)$")
+    target_value: Optional[float] = None
+    target_unit: Optional[str] = Field(None, max_length=20)
+    input_unit: Optional[str] = Field(None, max_length=20)
+    conversion_rate: Optional[float] = None
     target_date: Optional[date] = None
     category_id: Optional[int] = None
     color: Optional[str] = Field(None, max_length=20)
@@ -94,13 +135,15 @@ class GoalUpdate(BaseModel):
 
     @property
     def clearable_fields(self) -> set:
-        return {"description", "target_date", "category_id"}
+        return {"description", "target_date", "category_id",
+                "target_value", "target_unit", "input_unit"}
 
 
 class GoalListResponse(GoalBase):
     id: int
     uuid: Optional[str] = None
     progress: int
+    current_value: float = 0
     completed_at: Optional[datetime] = None
     created_at: datetime
     updated_at: datetime
@@ -115,6 +158,7 @@ class GoalListResponse(GoalBase):
 class GoalDetailResponse(GoalListResponse):
     steps: List[GoalStepResponse] = []
     reviews: List[GoalReviewResponse] = []
+    checkins: List[GoalCheckinResponse] = []
     tasks: List[TaskResponse] = []