rename: "Team" billing tier to "Family"

All literal "team" tier-value references renamed to "family" across
API routes, admin UI, OpenAPI schemas, and lib/tiers.ts. The DB enum
value itself is renamed in place via ALTER TYPE ... RENAME VALUE
(migration 0044) rather than drizzle-kit's auto-generated
drop-and-recreate-the-enum migration, which would have failed against
any existing row still holding 'team' — RENAME VALUE preserves
existing data with no cast/backfill needed.

Also adds STRIPE_PLAN.md — a full Stripe billing integration plan
(Checkout+Portal, tier→Price mapping, admin billing dashboard, and a
multi-user Family-group design since Family is meant to cover several
accounts under one subscription, not one payer). Planning only, no
Stripe code yet.

v0.47.0

packages/db/src/seed.ts

@@ -21,9 +21,9 @@ async function seed() {
         maxPublicRecipes: 99999,
       },
       {
-        tier: "team",
+        tier: "family",
         // -1 is the actual "no cap" sentinel (see lib/tiers.ts UNLIMITED) —
-        // pro uses large-but-finite numbers instead; team is genuinely unlimited.
+        // pro uses large-but-finite numbers instead; family is genuinely unlimited.
         maxRecipes: -1,
         aiCallsPerMonth: 2000,
         storageMb: 50000,