Rework balances around per-parent days left and deduce the partner from FK

Manual entry now takes one parent's sjukpenningnivå, lägstanivå and
dubbeldagar left (plus optional reserved days) and derives the rest in
build_snapshot, shared with the scraper. The scraper also reads the
family panel and exposes a partner deduction; with two parents it is
saved as a 'deduced' snapshot (migration 002). Parent count is the single
source of entitlement: one member gets 480 days and 96 savable at age 4,
two get 240 and 48 each. Workspaces are capped at two parents.

Also lands the in-flight squash of migrations 002–011 into the initial
schema and the removal of planning_mode.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

backend/app/models/workspace.py

@@ -15,13 +15,11 @@ class WorkspaceCreate(BaseModel):
 
 class WorkspaceUpdate(BaseModel):
     name: str | None = Field(default=None, min_length=1, max_length=100)
-    planning_mode: str | None = None
 
 
 class WorkspaceResponse(BaseModel):
     id: UUID
     name: str
-    planning_mode: str
     created_at: datetime | None
 
     @classmethod
@@ -29,7 +27,6 @@ class WorkspaceResponse(BaseModel):
         return cls(
             id=ws.id,
             name=ws.name,
-            planning_mode=ws.planning_mode,
             created_at=ws.created_at,
         )