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/tests/unit/test_config.py

@@ -39,3 +39,13 @@ class TestProductionJwtSecretValidation:
     def test_default_log_level_is_info(self) -> None:
         settings = Settings()
         assert settings.log_level == "INFO"
+
+
+class TestScraperDebugDumpOnSuccess:
+    def test_defaults_to_false(self) -> None:
+        settings = Settings()
+        assert settings.scraper_debug_dump_on_success is False
+
+    def test_can_be_enabled(self) -> None:
+        settings = Settings(scraper_debug_dump_on_success=True)
+        assert settings.scraper_debug_dump_on_success is True