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/entities/leave_wish.py

@@ -51,6 +51,21 @@ class LeaveWish:
     # completely unmodified.
     window_mode: str = "fixed"  # 'fixed' | 'flexible'
 
+    # §Decision A (co-leave, 2026-09-18 correction) — dubbeldagar are OPT-IN,
+    # never automatic, even when `parent_mode == 'both'` and the child is
+    # still inside the 15-month dubbeldagar window with quota left. Only set
+    # when the user has explicitly requested them for this wish. NOTE: no
+    # frontend exposes this yet -- the period editor's dubbeldag checkbox is
+    # not built, and there is no `wantsDubbeldag` in the TS types, so today
+    # the flag is only reachable through the API. When that UI lands it must
+    # show the checkbox only where `WindowOutcome.dubbeldagar_legally_available`
+    # says they legally could apply -- see allocation_service.py. Defaults to False so every
+    # existing wish (and every wish that never opts in) gets the new
+    # PL+vacation co-leave behaviour instead of dubbeldagar. Meaningless
+    # outside `parent_mode == 'both'` -- `LeaveWishService._validate` rejects
+    # setting it otherwise.
+    wants_dubbeldag: bool = False
+
     # Provenance of `name`: when a wish is created from a preset (Sommar,
     # Jullov, Höstlov, ...) this holds the i18n message key that produced the
     # translated string stored in `name` (e.g. "wishEditor.presetSommar").

backend/app/entities/parental_leave.py

@@ -30,7 +30,7 @@ class ParentalLeaveFetch:
     personal_data_uuid: UUID
     workspace_id: UUID
     child_id: UUID
-    source: str  # 'scraped' | 'manual'
+    source: str  # 'scraped' | 'manual' | 'deduced'
     fetched_at: datetime
     total_days: int
     days_used: int

backend/app/entities/workspace.py

@@ -9,5 +9,4 @@ from uuid import UUID
 class Workspace:
     id: UUID
     name: str
-    planning_mode: str = "solo"  # 'solo' | 'couple' — explicit, not inferred from member count
     created_at: datetime | None = None