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/routers/plan.py

@@ -83,10 +83,21 @@ async def sync_plan(
     user has pinned, and reports exactly what changed (`changes`) so the UI
     can show e.g. "Sommar 2028 flyttades 2 dagar — Ångra" instead of
     silently rewriting the calendar.
+
+    Doubles as its own eviction preview: when the re-derived plan would
+    silently delete another wish's days (a shared FP/vacation pool ran out
+    for that wish's parent), this call writes NOTHING and returns
+    `eviction_preview` describing what ran out and which days would go —
+    unless `eviction_choice` names one of the two caller-authorized
+    eviction strategies, in which case exactly that category is freed and
+    the edit is applied. No separate round trip for the common (fits-
+    within-budget) case; see `PlanningService.sync_plan`'s docstring.
     """
     scope.check_workspace(payload.workspace_id)
     try:
-        result = await service.sync_plan(payload.workspace_id)
+        result = await service.sync_plan(
+            payload.workspace_id, eviction_choice=payload.eviction_choice
+        )
     except NotFoundError as exc:
         raise HTTPException(status.HTTP_404_NOT_FOUND, str(exc)) from exc
     except ValidationError as exc: