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/.env.example

@@ -17,6 +17,9 @@ APP_SCRAPER_ENABLED=true
 # set to actually enable saving.
 # APP_SCRAPER_DEBUG_ENABLED=true
 # APP_SCRAPER_DEBUG_DIR=./debug/scraper
+# Also dump the same artifacts after a SUCCESSFUL extraction (not just on
+# error) — useful for confirming FK's real DOM. Same warning applies.
+# APP_SCRAPER_DEBUG_DUMP_ON_SUCCESS=true
 
 # Database (default: SQLite in repo root)
 # APP_SQLITE_PATH=./foraldraledig.db